Are you married to the idea of a Kerf? Lotsa discussion on whether there's any real benefit as the efficiency is all about the ratio of wall for the amount of port area. An aero has the best efficiency (least wall to port area + flare to minimize possible port noise), then round, octoport, square, then slot port. You have what, 87in2 of port area figured?.. I'd say you got any port noise just about buried for good... that's a TON of port area. IMO unless you have close to absolute minimum port area for your power, then a kerf could be used to possibly minimize the possibility of port noise. Otherwise I feel that a basic 3/8" or similar roundover with a router will be fine. Sure looks good when done correctly and doin' a kerf throughout the length (if bends are present) might increase efficiency somewhat, probably does, but I've heard so many claims that I digress... lol... for anything I do designs for I try to keep it as simple as possible, people do the d*mdest things! I've seen people use the wrong thickness of material, try to re-size it for their vehicle as their measurements were off or just cant read a tape... etc. Looks like you probably are comfortable doin' this so "NIKE" it! I'd try to increase the "effective" port length a few inches (my personal taste in tuning... that's all).
I played around with it and I guess I was incorrect... looks like it'll be around 26" long if that's how the measurements work out for you below...
What a PITA, that's why I don't do these... but once or twice for my own stuff maybe someday... but otherwise NO... lol
Best guess I got is a 37hz tune in 5ft3 net... good luck