First find the best hose routing. To do that:
*First mount your bc or backplate and wing on a tank.
*Remove all the hoses and port plugs from the first stage.
*Install the first stage on the tank valve.
*Install the primary second stage hand tight.
*Follow with the secondary second stage, inflator hose and SPG hoses.
After you've found the best configuration, torque down the hoses and install the port plugs. Note that some first stages only have one HP port, so that might limit the options you have. Now it's time to work with your buddy in a pool. With your equipment on have your buddy take measurement and then purchase the correct lengths.
Before you settle on hose lengths and routing configurations, spend a little time reading in the
Hogarthian Diving forum, you'll pick up some great ideas.