I have a DD SST50 from Dave. Mine will run for a while on high before it's too hot to hold, but it will dim quite a bit as a result. I can't imagine the SST90 would fare much better. I got the three mode one, so I use high for short bursts and med for extended runs and it seems to work fine. The key is to make sure its in a good metal host to move the heat. In hindsight, I probably should have gone with the regulated one for more consistent brightness. Maybe there will be a DD SST50 up for sale soon...
As far as that triple XPG,
! That in a 9P host would be killer! Wonder how hot that one gets in comparison? The review links are no longer valid (maybe due to the lost posts recently?)