So how did you do the cutouts for the hitch? Can you post any pictures? Thanks.

Trailers are hardly universal. If you have a trailer with a flat floor, put a level on the floor and see what height the tongue wants to be. Then you can determine at what height your ball needs to be.

I run the curve, as shown by ipd, up, so the ball is above the top of the receiver, but not much.

The Volvo ball hitch should be the straight one. The reason the trucks have the curved variety is because the hitch mounting location on a pick-up is so high that the actual hitch point, i.e. the ball, must be dropped a bit so that the trailer is pulled as level as possible. If the truck used a straight shaft, the trailer would ride at a high angle which would throw the balance off, cause it to fishtail maybe, etc. On the other hand, the hitch mounts much lower on a Volvo, so you need a straight shaft. A "curved" shaft (which is used to off-set and lower the ball) would place the hitch point much too low.