considering that all the sim.s say it will stay below mach even with rounded edges...yes I was planning to leave them square, it will also keep the altitude down should I get the urge to stick a big motor in it .
Looks good to me - I like the fins, although the 90 degree trailing edge close to the base plate might make them vulnerable to chips on landing. At first I thought the root chord was a little narrow, but it's an optical thing - I see the height and root are the same. The speed / altitude seems credible, commensurate with what I've got out of a similar 4" on 38mm J motors. Just another small point - the fillets on the .ork file are currently listed as cardboard and 0 radius - I'm assuming you'll be using epoxy and giving them some radius (...?)
I 'borrowed' the fin shape from Stine's book(had to adjust the formula a smidge for HPR, else they would be Huge). got some parts in the mail today (centering rings and av-bay)...now the fun begins, cutting things .