I am jealous you have a Honda power plant the way that I set my jet units up is I set the intake as far back as possible if the hull has a small v at the transom put a pad in the hull about 4 foot long start at the keel level and make it just wide enough at the transom for the pump to sit flat...
just use the Yamaha jetski intake and you can get an impeller to match your motor I am running a yammie pump behind a kawsaki 12f 4 stroke be running it that way for years just my 2c will
it sure is funny the guys that say its easy to build one and they do it and use one the river once and then you see on craigs list the next week for sale and you them about the performance and they tell you it works ok if you know what I mean lol will
here are some pics of a boat that I built for a friend it uses a 650 Yamaha motor and a wet jet pump stick steering with trim the top is rhino lined and the sides and bottom are painted