Here's a little design detail I often use when designing things to fit snugly together in a 3dprint.
For joinery like these dovetails I'll put a few little "tension bumps" in the friction-fit area to optimize the fit. If it's too tight, it's easy to tune the bumps with an exacto knife or some sandpaper.
I tend to shoot for about 0.3 – 0.4mm clearance for a clear but snug fit.