So, in theory one should be able to use a venom sack to help even up that size difference between them and the target, but if the target is using a venom sack too it really negates it.
What I propose is a max size so that giants can't get any bigger than they already are. That'll keep from many fights just consisting of bash/bash/bash/bash/bash...you get the point.
That also eliminates warriors from having their advantages vs non giant non prot shield classes. In an attempt to make it easier for some, your making it harder for others. This will actually take less power from pure lagging melee who are already going to have trouble vs casters of similar skill and eq.
I believe your making an honest effort at a good contribution to the game, but there are other ways around avoiding bash. Most smaller creatures are either A)qrace/class wannabes or 
high dex or high con. In all of these cases there are ways to buff ac. I can think of several items that are 20-50 ac each, (2 neck, 1 legs, and 2 weapons and a shield all spring to mind) so I would suggest more buffing your ac and enlarging. It is not often that you die to a perfect lag lock (outside of crusaders, and barbarian monks and zerks) really the classes that suffer from this the most are going to be rogues, which this is a case of giving them a weakness. The last thing you want is a drow ninja who is always able to get away despite failing an assassination. You need to be able to lag some classes to keep the playing field level.
This is interesting.
If you limit PC size to giant, this means that some classes get a safer times vs giant lagger.
Interestingly this also affects monks in dragon stand that no longer can get Titanic size.
I thought there was a step up from giant already. So even if max size was capped, if the giant and the human both eat a sack, nothing changes.
edit: I misread the original post. Do things that are already bigger than giants get to remain so or is Giant the new cap size you are suggesting?
Well the largest natural size of races. Pretty much I suggest that giants should not get the benefit of enlarge.If the giants are using it also it really negates the purpose of smaller races using it. All it does it create a wider gap if the smaller race doesn't have one and create a need to basically ALWAYS have it and I've met newer players who don't know where to get it or what item does it.
As far as oh, get more -ac and "I can think of items". I already discussed getting -400ac and unless you're JIBBER apparently it's not happening for you 
Props Jibber, you should own stock in FL.
Yeah and tell me when these pieces of eq are in or pretty much any rares besides elemental bracelets besides maybe that day when rare purge happens.
The original post is a bit misleading.
Now, I don't know how the bash formula exactly works, but from my personal experience, I've had a giant bash me (halfling) and sometimes the bash lasted four rounds and a half (VERY close to five) and sometimes it lasted one round (note that I have no idea whether they ate a venom sack).
Of course the cases where it lasted one round are much less than the cases where it lasted almost 5 rounds.
From the huge lag difference I have experienced, I believe there are more variables that define the lag you get from a successful bash. I actually believe that the bash formula is quite complex and there are at least a couple more variables than just size and AC. Actually, from a recent discussion it seems like being mounted also gives an advantage in bash avoidance.
No matter the variables though, being bashed and getting ~5 rounds lag from it is ridiculous. I am strongly against capping PC sizes up to giant, but I am FOR changing the way bash formula works. One should no be able to be bashed for more than 3 rounds. There should also be diminishing returns from stacking bashes. That does not mean bash should have more chance to miss, but it could mean less lag.
Also, no matter how much people claim get AC and you will be safe, that is not the case really. Getting -400 AC is not easy as a melee/rouge/hybrid, even with -100 AC from buffs alone. Hell even -300 is not easy.
That being said, when my DECKED halfling blademaster died to Grum, he was bashed 4 ticks in a row without him missing a single bash. It is funny, because his DIRT was missing 50% of the time while his bash was landing with surprising efficiency.
Just my 2 cents.
Viri said he had capped Bash to max 4 rounds of lag, due to Halfling complaining that they were having time to drink a cup of coffe while waiting on lag to pass.
Dind't your halfling have DeathWeaver or something to counter bash?
Enlarge only lasts a very short while. I do not see it as a problem. Over many giant melees with great hit/dam, ac, and luck I have had many small races evade my bashes/slams/crusader skills. Probably the best in this department was Myrtaal. I missed the lag attacks on him so often I nearly gave up with them..........