WL over or under chine?

This might help

 

No keels or centre-boards ?

 

Yet to decide. Some days one center board, another LARs.

 

You have full stern sections, the bow will need to be reasonably full to balance that, a blunt half-angle at the bow will push a lot of water up the topsides, and give you a wet boat.

 

Here is front quarter view
The front tramp is attached to a 12cm wide rail along the hull designed to turn the spray down, not shown in the pics.
#2 shows cutaway just fwd of the cross beam, not sure of your reference to blunt angle.

 

Your best plan would be to post the lines in plan and profile views, to get some comments from sailing cat experts, which I don't profess to be !