These effects, in general, feel a bit too strong; though it depends on how restricted you are from just including random rationals in your deck. Like, if you can just put a 29/71 in your deck, you kind of just win on the spot. Then again, with how your energy costs would be way lower, I guess the game would have to be balanced around you only having like 2 max energy instead of 100 anyway.
/11 is an interesting effect; I can see why you didn't want to just make it frozen opponent pieces, but it feels a little weird.
What's the exact opponent stone that gets added by /31?
Also, because you didn't specify, here's what I'd do for the other low prime squares:
/49: Cannot be placed if there is any fire on the board. Freezes itself.
/169: All opponent cards cost 169 less and all of your cards cost [this card's cost] more.