Hârn (regardless of version) has always been designed for normal humanoid creatures.
Exactly. The system is designed pretty well when humanoid sized creatures are used. The HM systems as played treat large creatures as having a lot of "hit points" which is ironic because it is what HM was designed to get away from.
Large creatures tend to have better natural APV so larger creatures will more often get minor injuries when hit than serious injuries
Sometimes, often, but not always do larger creatures have better AV.
There is a system I have used that IMO works well in representing larger creatures, and fals very much in line with HM mechanics, though it requires some changes in the bestiary.
It's a "size factor", where every "beast" is given a size rating depending upon body mass.
I use 150 lbs as the basis for a size of "1". Every doubling in mass adds one to the size factor. For many beasts, it's easy to find similar animals sizes, but for the more fantasy types it has to be guessed at a bit.
But we have based on mass the following sizes:
150 lbs = 1
300 lbs = 2
600 lbs = 3
1200 lbs = 4
2400 lbs = 5
4800lbs = 6
Here are the changes to bestiary stats - all creatures are then given a relative "strength". This is a base number, usually in the 9-12 range or so. Most herbivores get a 9-10, Carnivores a point or so higher, cats about 2 points higher, avians are at the top end, maybe a 13 or so.
This strength is mulitplied by their size factor - fractions are OK, I.E. a 900 pound beast would be in the 3.5 range.
Will is as HM, Fatigue is different. Just because a creature is huge does not give it a huge fatigue rating - i.e. a dragon might have a fatigue of 13-14, not 50 or so.
End is then determined by adding the 3 together and dividing by 3. I also then subtract 1 points from endurance if size 3, 2 if size 4, and 3 if size five. No real reasoning here, just seems to work out better.
Armour is determined by both size and armour type - many animals, such as a horse, lion, etc., are just hide - not armour value for this. However, they do get a size factor for armour, which I give as their size x 1 for B and E, and .75 times size for P (Thicker limbs resist being cut deeply more, a thicker body offers resistance to piercing but not quite as much).
Some animals have armour that may be similar to armor types - however some have to be guessed at a bit.
The other thing I do - Injury points (not the effect on stumble/fumble/shock) - their effects are reduced to 1/2 for creatures in the 2-3 size rating, to 1/3 if a 4+ size rating. So a size 2 creature needs 20 points of injuries to get a -10 to ML's - a size 4 creature needs 30 IP's to get a -10 mod.
Hru - Size 6 (I use 4800 pounds, not 3 tons) Will per HM 13. Fatigue - I don't see a Hru as having incredible stamina, go with a 12 or so.
Strength - 11x6 = 66. 66+13+12 = 91, divided by 3 = 30 (-4 for size) = End of 26
Armour - I give it HM3 Kurbul to represent the toughness of skin and body as represented in HM3, so a 4-5-4. It's size gives it AV's of 6-6-4, so overall armour is 10-11-8.
So overall, It's a creature with a 66 Strength, 26 End, and 10-11-8 armour values. Of course, Penalties are reduced to 1/3 from Injury points.
Lets take a Dragon - (2400 pounds, it can fly, imagine a bit light boned) Size 5, Will 19. I give it a good endurance of 18 as an avian. Strength is 13, high as an avian, so 65 strength.
End - 65+19+18 = 34 - 3 = 31 End
Armour - I give it HM scale. It's thicker probably than HM scale, but this is already pertially factored in by it's armour for size, so 5-9-4 + 5-5-4 = 10-14-8
So a Dragon is a creature with Strength 65, Endurance 31, and 10-14-8 BEP armour.
How about a mundane creature or two?
A very large warhorse, weight 1200 lbs. size 4. Will 12, Fatigue 12 (better than human, not exceptional) Strength I go 9, so 36.
36+12+12 = 60. 60/3 = 20, -2 for size = 18.
Armour is 4-4-3 for size, I give it nothing else as it is normal hide, thickness taken into account by the size.
So we have Strength of 36, Endurance of 18, armour of 4-4-3, and it take 30 Ip's to get a -10 mod.
How about a large Grizzly type bear? A good sized male will weigh about 600 lbs, not a huge one but decent sized.
Size is 3. Strength is 11 as an omnivore, overall strength 33. Will is 14 (aggressive male type), fatigue is 12, nothing special.
33+14+12 = 69/3 = 20, -1 for size, or 19.
Armour - Size gives it a 3-3-2. It's thick fur I look as inferior HM quilt, or 4-2-1, so 7-5-3.
So a grizzly has strength 33, End of 19, and 7-5-3 BEP. Plus IP's are haved when determining EML penalties.
This makes the real large type creatures animals that can take a fair amount of minor injuries without being slowed down. But it also makes it possible with a very good blow so seriously injure them, but they won't be reduced to blobs that cannot fight hardly at all with a 15 EML, just taking blows til they collapse.
And if you really want to represent large creatures well - I'd suggest using HMGold's Press tables, and also their foot vs mounted and vice versa tables.
The Press makes it tough for a human to do anything but dodge - or counterstrike and hope they get real lucky. Otherwise, they will be in close with a large crature, a real bad spot to be in.
Also, the foot vs mounted makes the danger of being trampled by these larger beasts very real - even if they are not intentionally trying to trample their opponents. I consider the larger creature "mounted" if there is a 2+ size difference between the two.
We have played combat like this a few times with large creatures - and it makes fighting one a totally different experience than fencing with a humanoid. Scary, but they can be taken down.