Hi, i am not that an expert, but personally i wouldnt put the 2nd chan in the FX-Loop of the triaxis. Using the Triaxis as a mono-output preamp basically is right (and no, the triaxis doesnt generate a stereo signal at all by itself) i would put normally after the output and then go from the ISP in the GMajor. Mono of course, since the signal is naturally mono from the Triaxis anyways. One other thing: Be sure you have the so called 'Larry Mod' in your ISP ProRack G. It consists of 4 resistors which have to be placed on the main PCB of the ISP, it corrects the time vector processing to be much more accurate. If you need more Info see this page from ISP website: http://www.isptechnologies.com/decimatortimevectorprocessingmod.htm
everything is explained there. I have done the mod on my unit myself, it is very easy to do. Okay, good luck with your setup. Send some pics in the gear thread! bye!!