Hey there...I had the same issues with radio box clearence on the sv. I would poke around for different headers and go with the quiet pipe as it should brind your tip out of the rear of the boat. The one ms hydro pointed out from hpi almost worked for me, but I cut too much off by mistake and couldnt find another. I was trying to cut an angle into it that would direct it away from the radio box but I botched it up. So I ended up with an associated truck header, heated it slightly, (low, blue flame, only for a couple of seconds) grabbed it with a shop towel and put a little bend into it. I know it's a different boat, but here's some pics to give you an idea....you may even be able to bend that os header you already have..had to enlarge the exhaust exit hole a little bit...on inside of hull I ca'd a graphite piece from a rc boneyard car, shaped it to fit the black insulation tube that exits the transom, then siliconed it shut.....had to trim a little off my box too....I may tweek the angle more later to give more clearence of the radio box and open the hole some more, but, it all works just fine now...I cut an exhaust coupler into 1/3 and slipped it between the pipe and the box for now...winter project to move the exhaust again...starting to feel like fall already....
***Now that I am awake and coherent, yep, what msvegas said...wasn't thinking, you're boat is longer...
looks like a tight squeeze so an extension off the exhust tip will def be the way to go...the header is something you'll have to play with either by cutting or heating/bending....that's gonna be a whole new boat with that combo, like night and day
Once you get past your clearance issues, the rest is cake....