Grand Beastform Mutagen / Beast Shape III special ability DCs?

[GraphiteGolem]

This might be a silly question, but I couldn't find any sort of answer for it, so here goes:

When casting beast shape III or higher, or using the beastmorph alchemist's Grand Beastform Mutagen ability and taking say, poison and web, which have DCs (or HP, in the case of web) based on Hit Dice, do you use 1/2 character level, class level (for alchemists this seems like it might be the case, but there's no language that I've seen supporting this)?

[Krinn]

I would use 10 + 1/2 total level + CON modifier per monster rules.
Web HPs do not follow a formula, but 1/2 total level + CON modifier seems ok.

[Seraphimpunk]

it uses the spell's DC per polymorph rules.

so a witch that casts vermin shape II, uses the DC of the spell ( aka based on what level spell it is for her, + her int mod )

so an alchemist would use whatever his typical DC calculation is / or what spell level equivalent it is for the class.

Magic Section > polymorph wrote:

If the form grants a lesser ability of the same type, you gain the lesser ability instead. Your base speed changes to match that of the form you assume. If the form grants a swim or burrow speed, you maintain the ability to breathe if you are swimming or burrowing. The DC for any of these abilities equals your DC for the polymorph spell used to change you into that form.

not sure how the hp of the web will vary. but poison DC will be based on the spell/infusion used to transform.