Not-so-recently, I bought two sets of 20mm AB Figures for a 1/72 WWII Jeep (Italeri) and an Sd.kfz.251 (First to Fight). The figures are wonderful, very well sculpted and scaled to the vehicles, but they just don't fit in the vehicles!

Neither of the sets are specifically made for a Jeep, or for a Hanomag, so maybe that could be the issue, but nonetheless I've got these now so what can I do to fix that and make them fit in the vehicles?
For most of them, the issue is that the knees are at basically a right angle, so their butt is floating above the seat. Quite a few of them, though, have legs and feet that just don't fit inside the Jeep, not just height but also length-wise.
I could try and make the seats bigger with greenstuff (although the vehicles are already painted) for those with a smaller gap, but especially for the German fellas it's about 3-4mm, I can't really add to the seats, or their butt

For the Jeep guys, their feet (for those in the front seat at least) are not super visible so I could chop them up, but in the Sd.kfz.251 their feet are visible, and I'd have to chop so much anyways I'd end up removing anything below the knee.
I wonder how the dedicated sets for these vehicles are sculpted to account for this. I'd imagine they're a bit more cramped?
What do you advise me to do in this case? Anyone ever dealt with that problem before?
Thanks in advance!