Dyneema is just fine. Just set up your pole with some noticeable prebend and the creep will only relax it a little bit. Dyneema has about 2 % creep I think but after that has settled it won't stretch any further at all. So compensate for this by making your lines a little too short initially. Only a little !

Besides I've been hanging (trapezing) of 3 mm dyneema (hard outer mantle) for many seasons now. Using a fishermans hitch and bowlines. Also my spi luff is handing off a 2.5 low grade dyneema line. The lines haven't given way yet. Mind you I hate spectra with a passion. It is nowhere like true dyneema in my opinion and it will snap.

D12 versions of dyneema (the new rage) are very slippery on the outside and these line have inferiour knot holding characteristics. So just go for the plain dyneema with hard outer mantle (also cheaper) and you are set.

Wouter