You have to make sure levels arent loading as you go.
Otherwise the import will fail wen the Vram hits that limit.
In 4.25 it was literally enough to close the levels/minimap panel out to achieve a succesful import.
If the newer engine versions aren’t working (which is possible ofc), I’d suggest you download something like 4.18 and try the import there (4.18 is before the landscape system was given a the first whack that has made it work badly).
After a succesful import you should be able to upgrade to any engine version (it will literally just be tiles).
I’ll try and do a 200km import in 5.2 just to have a laugh myself…
Also just note that crashing during import is pretty common when dealing with tons of tiles regardless of overall size.
I think my uninterrupted import record was 2211169 tiles.
Obviously the end result was something that couldn’t work just due to the sheer number of drawcalls for impostors (not to mention the size on disk of the levels).