I clamp heel to tail in order to make sure the neck seats correctly, because sometimes the heel does not always sit flush with the body, as it seems the force of actually clamping the neck to the body wants to push the neck the other way... it makes for a seamless joint and normally very small amount of force is required... but for whatever reason there's always that gap on one side of the heel that will close when I dry fit them, but remains open when glue is applied.

Hi Tai,
Ukuleles are supposed to be a fun build. If you are not having fun then you are doing something wrong. The shapes and sizes can be just about anything.
The last Uke I built used a neck from a homemade mandolin banjo someone gave me. Part of the fun was figuring out what to do with the extra holes in the peghead. It was a soprano scale mounted on a concert sized body -I joined it at the 10th fret. I used some small pieces of rosewood for the back and sides. Is it a world class Ukulele like Bob Gleason builds? Definitely not. But it plays reasonably in tune and someone will have fun with it.

for whatever reason there's always that gap on one side of the heel that will close when I dry fit them, but remains open when glue is applied.