re: New mitre sled

Brian
The issue is that both fences are off 45 DEG. your frame mitres work good and that indicates that the fences make up 90 DEG.
On my sled I can compensate in two ways I can set the fences to a perfect 90 DEG. by loosening the bolts and adjusting it and also rotate the complete fence assembly to get a perfect 45 DEG.on both sides .
I would make the fences on yours movable and use a good drafting square to align them to the blade body not the teeth .Also a stop with a dowel attached may help you to get better precision as you are not aligning on the tip of the mitre but somewhere on the face of the mitre .