RE: First time speeder needs help
You got a couple options, you can use the Hayes Beam mount. This works fine, and has the same bolt pattern as the Nelson Backplate.
Or, Lewis Schwabb sells a couple different (round and square) kinds of backplates that mounts to your exisiting backplate. It will be tight getting the fuel line on and off the remote needle, so its easier to just put a 2-3" section of fuel line onto the nipple and then use one of those little plastic L joiners to your fuel tank. Unhook at the joiner to fuel the tank rather than at the nipple. The square one is my preferance because it has the same mounting pattern as the Nelson. The problem with this backplate is that you will need to take a dremel to the remote Needle mount to make room for the bolt (not a big deal). The round one gives you room, but its a different bolt pattern than the nelson.
For a simple sport model, I'd go with Hayes, and mount the engine as far back on the beams as possible.