Recent communications with customers suggest the White-Strong-Flexible material is more than suitable, but does need a primer-filler (Auto-shop, 'Duplicolour') paint to smooth out the 'powdery' finish. The holes in the tank ends are there to allow excess material to escape that are used in the manufacture process. But I've supplied two tank end-caps on a sprue, so they won't get lost in manufacture. Wheels have now been 'fixed' to prevent manufacture problems. My thanks again to Prof. Bill Guegold for the first images of these models ( Frosted Detail material) shown with a Con-Cor tractor cab (not supplied).