Yes we have both -- fashioned the contours with Bondo attached adhesive backed abrasive, very simple works great. We actually make our J185 and J200 tail blocks on our CNC machines --- stacked laminated glue ups.

Mine's a bit clumsy but works- T shaped board clamped to the linisher (belt sander) table, swinging arm with a bolt locating various radius points.
Vertical plate on the end off the swinging arm gets required block screwed to it.
Start linisher, swing arm with block.
But sometimes I just mark the radius from the mold on it, use a block plane and finesse it in the mold with abrasive, less hassle than setting it up if it's just one at a time.

Ken, are you talking about a sanding block like a fret board sanding block?

Timely thread. I just revised mine so I can radius a headblock with the fretboard suport attached. I also put a spline down the center to keep the two pieces aligned.

As opposed to tail block, I suppose.

That makes sense --- but again, the term I learned was "end block"

Ok, I can see radiusing an end block, which I free hand on a belt sander. I can see where the jig would be a step up, But I always thought a neck block should be flat were the neck meets the sides. Am I wrong? (again)