Well about 40 of those layers I could delete now. I also use some layers like masks multiple times, so probably another 30 of those layers are duplicates. Then there are separate layers for things like spoked and covered wheels, so I can just turn these layers on and off as needed. I'm just being a bit lazy here, on a 4096 by 2048 res skin I would be more careful about layer management and delete the unused layers as the file can get so big it makes PSP chug towards the end of the build even on a fast PC with lots of memory.
There is one thing that I don't like with X9 compared to v5; on the earlier version the mouse wheel zoom worked much better. It would zoom down to precisely where the mouse cursor was, while on the newer version it zooms to a point somewhere near the cursor and won't zoom into a corner at all. I find this a constant irritation even years later. Having said that the much larger tool size and superior memory handling more than makes up for this drawback and I wouldn't go back now even if I could.
The only time I have had X9 crash is if I try to use the mouse wheel zoom at the same time as I am dragging an object. Now that I have trained myself not to do this it works fine.