It's probably the wing tubes in the hulls. Adding a set of ports makes this not to bad a repair job. A quick check is to fill the tubes with water and see if it leaks into the hulls (mine did). Hint, don't glue in the ports until after the repair is complete. It gives you a lot more room to work.
Excellent way to test the leaks. If the tubes need repair, 5inch ports are the way to go- definitely do repairs before you install the bezel that the port hatch screws into.
Also try this: duct tape a vacum to blow air to the the drain holes to lightly pressurize the hulls, if it is leaking anywhere else you may be able to hear the air escaping.
If you have leaks in the tubes and are able to leave the wings on for extended periods put a bead of clear silicone around the deck where the wing support goes into the tube.
The 17 is pretty light - I would think that your trailer would work fine with a couple cross bars mounted on it. Get a a couple 8 foot pieces of square-channel or whatever and mount rollers and guides on the ends - attach to existing trailer with U-bolts. I know someone who carries their sunfish under their 16 on the sunfish trailer. Don't forget - you need a mast support on the tongue also.
I say go for it - Just like my Hobie poster says