A helmholtz resonator is really easy to make, it's harder to explain it to your local shop, than it is for them to make it. Most guys are gonna look at ya like you're crazy, I know that's what I did the first time I was asked to make one. Now, I've literally made hundreds of em for several different applications, including Raptor's. They're just a 26" (or so depending on the frequency you're trying to cancel out) piece of tubing branched into the exhaust system and capped on the end. There are a couple of different formula's used to figure out the length. There is helmholtz math, and 1/4 wave math. I've tried both on a Raptor, and they both work about equally as well.
As far as exit location, it's pretty negligible where the exhaust exits (between the 2 choices you've presented) Either exit will work equally as well when comparing HP and TQ, the sound will be slightly different, but the difference there is just a matter of preference, there is no right or wrong answer there either.
The thing to consider that IS critical is the design/engineering standpoint. You want a system that doesn't stray too far from factory dimensions. That's why I always say to do either a simple muffler sway, or a simple bolt on which maintains factory dimensions as closely as possible....yet removes the factory restrictive muffler for either straight pipe, or a muffler similar to a Borla or BAmuffler.