Ah, got it ... OK, I found the TEC control, fiddled around with it a bit, no difference. You're saying that the minimum ADU was just a few thousand electrons off of full saturation, which for an exposure with the cap on makes the sensor useless for actual work (even if I set a pedestal to something crazy like 63400) ...
(sigh) So, I'll stick a fork in this and call it done ... SGP works very nicely with my D90 and G3, just not with the 8300 ... Maxim works nicely with the 8300 and the G3, but for some reason (even with the DSUSB) can't do an exposure longer than 30 sec like SGP and BYN can do ...
I'll use the proper tool for the proper instrument, I guess ... thanks much for your help, I've learned quite a bit!