Thanks for the reply. A second hand Aptus 75 does indeed seem to be the best price/performance combination out there.
Will the dynamic range be worse at a 32 second exposure compared to 1/100? That is, is there noise buildup in the longer exposures? I could live with the 32 second limit if performance is good in the whole range, but if there is a drop I'll probably have to look for P25+... or lower my standards :-). P25 does not seem to be that good at long exposures either, and may have some issues with newer CF cards it seems.
You may look also at the Aptus 65 which feature IDENTICAL sensor to Aptus 75 but a 44x33mm crop instead of a 48x36mm crop of 645, and proportional less MP from 33 to 28. It was cheaper when I bought mine years ago, and may possible be more affordable than Aptus 22. The Aptus 65/75 is one generation newer than Aptus 22, or one older than the 40/56MP Leafs, or two older than the 80MP.
If indeed it is for a tech camera, the slight lesser crop may not matter. That said I managed to focus the Aptus 65 on a custom made stitching adapter on a Shen-Hao with 72 XL and 150 Sironar-N non digital lenses, although I did not use that combo much. My stitching adapter had a Maxwell High-Lux groundglass.