Ok I got me ConvImx now, running it on all .bmp texture files in my CIRP installation after having successfully test-fixed half of the PAKT CIRP office.
Will let you know how it went when it's through, but: if it should be that easy, why hasn't anyone else done it before? And: should I make updated scenery zips available for upload at RTMM?
EDIT: Fixed the PAKT CIRP office for good - will fly to all the glacier stations again the next couple of days to check them out. Also good for the Antonov-2 to get some air time!
Have to emphasize my offer: as it seems to be rather simple, I offer to give back any modified/fixed files for update on RTMM.
EDIT2: Yep, definitely fixed my invisible-object issues! Thank you guys for pointing out this tool, wonder why I didn't come across that one before. Here's a shot from the first legs I did today, the Antonov doesn't like the kind of cross winds you get up on the glaciers, but that doesn't matter really - it can land directly on the parking field, nose in the wind
(ok, not done in that screenshot, but at station #10)