Yo dude,
I don't want to lower morale, but I personally wouldn't risk drying my resin at those temperatures...just to be on the safe side. I use a heat mat, the kind used for reptiles, bought off Ebay, which is perfect.
Obviously, potency of your resin depends entirely on the potency of the cactus you are working with...however I have used this tek with profoundly successul results.
I used a homegrown Peruvian torch, that wasn't particularly old, so I didn't think it would be particularly potent. Also, I was at university when the resin was drying, so it was exposed to the heat mat for 3 days, when it was likely already dry. Thus, working with this likely not particularly potent cactus, and heating the resin for a prolonged time, I didn't think my resin would show much activity. However, unlike everyone else here it seems, my resin dried to this hard, crystalline, glass like consistency, which made it easy to powder and put in capsules.
However, 2g of this resin was the most potent extract of cactus I have ever ingested. It was stronger than 250mg of torch acetate, and it had a smoothier and fluffier high, with a more pronounced body high that was very pleasant. To be honest I would have considered it too good to be true, had I not experienced it myself. Of all the expeirences I've had with cactus extracts, this also produced the strongest euphoria, being very similar to MDMA. So after this experience I am a fully fledged resin convert...