Come back with your shield... or on it.
 

The following are my replacement rules for shields.

IMO absorbing incremental points of damage is not how a shield is supposed to function. Their primary purpose is to block the hit entirely which is best simulated using DX penalties in TFT.

BUCKLER/MAIN-GAUCHE -1 DX to be hit
SMALL SHIELD -2 DX
LARGE SHIELD -4 DX
TOWER SHIELD -6 DX

Some may notice how nicely this now aligns with the existing 'concealment' rules (ITL page 122).

Note: When the shield is used offensively (i.e. shield-rush or off-hand strike) this bonus is lost.

Re: Come back with your shield... or on it.
 

One possible problem is that this scaling runs away for large and tower shields, making it basically required to fight with them. If I can take a -3 DX penalty while imposing a -6 DX penalty, I basically have to do it, no matter what else is going on. If both sides do this (as they should), all melee combat is fought at -9 adjDX. Oof.

Re: Come back with your shield... or on it.
 

That is true, though it is worth noting that shields (as well as armor) have ST requirements in my game which keeps the number of heroes running around w/ tower shields somewhat manageable.

SMALL SHIELD requires 8 ST to use effectively
LARGE SHIELD requires 10 ST
TOWER SHIELD requires 13 ST

It is also possible to mitigate some of the shield penalties using talents. My revised version of SHIELD EXPERTISE, for example, reduces the DX penalty by 1.

Re: Come back with your shield... or on it.
 

Shields, armor, and weapons are already limited by weight, though not to the levels you indicate. It takes a ST of 9 to carry a Tower Shield in one hand.

Re: Come back with your shield... or on it.
 

Except being able to use a tower (or any) shield effectively requires more effort than would simply carrying it around. I also tend to use a more abstract approach to encumbrance and find that using minimum ST requirements for things like armor and shields is simpler.

Re: Come back with your shield... or on it.
 

Whatever the details, this looks to me like one of those house rules that introduces a significant enough advantage to a piece of equipment that it stands out against the background of generally balanced gear, and so becomes necessary (assuming you are trying to win).

Re: Come back with your shield... or on it.
 

I hear what you are saying, Lars, but this isn't a scenario that seems remotely desirable outside of arena combat. Tower shields have a place on the battlefield, but are rarely practical in the labyrinth.

Re: Come back with your shield... or on it.
 

What's the stats for the Gou-Rang?

https://www.youtube.com/watch?v=RXYltNPlMaM

Re: Come back with your shield... or on it.
 

I've done some playtesting with a similar house rule, but I simply used the RAW hits stopped as the DX penalty to be hit. That way the original balance is impacted less.

I think:
DX penalty = (RAW hits stopped +1)
may feel about right to me.

Re: Come back with your shield... or on it.
 

We started with the same, more moderate, 'to hit' penalties, but in our playtesting the conclusion was that the shields didn't feel shield-y enough (how's that for a technical term?). Plus we also agreed that the opportunity cost wasn't quite balanced since using a shield means giving up a second or larger, more damaging weapons.