Personally, the whole splitting until there's 64 llittle 1 HP black puddings sounds like a tedious job for combat, and boring. In all honesty, I'd allow the pudding to split as many times as it has whole number Hit Dice. 8HD to start, 4HD (2), 2HD (4), 1HD (8).No more spliting, after that it just gets silly. The end result I'd handle this way:
AC 3; HP 115; +8 melee (2d6+4 and 2d6 acid, slam); 1 (huge) creature
AC 4; HP 57; +4 melee (1d6+2 and 2d6 acid, slam); 2 (large) creatures
AC 5; HP 28; +2 melee (1d3+1 and 1d6 acid, slam); 4 (med) creatures
AC 6; HP 14; +2 melee (1d2 and 1d6 acid, slam); 8 (small) creatures
The AC adjusted to sz modifier, HP split as normal (roudn down), melee reduce acorrding to HD split so creatures base +10 (-2 huge sz mod), split in half for a +5 base (-1 lrg sz mod) for a total of +4 and so on.
I split the creatures base damage as normal leaving the acid, slam damage as the acid will still hurt alot regardless of size, but eventually reduces as the size reduces because there's just less of it. Anywhow, just how I'd do it as an example for ya. It's alot of work to have to do as a DM to run the creature but it's definately interesting and I'd like to see the look on my player's faces when it "splits" doing no recongnizable damage, hehe.
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