There is only one style of spreaders for a Hobie 18 - they have minimal rake adjustment determined by positioning a pin in one of the spreader arms. Virtually all racers run with the spreaders raked as far back as possible (there are only like two or three possible settings).

As far as diamond wire tension, if you have a comptip, you want to run the diamond wires snug to tight (sorry, don't have a quantative number). 18's are pretty underpowerd boats by today's standards and the comptip is quite flexible, so you want to stiffen the lower part of the mast as much as possible to keep some power down low.

Shrouds should be snug enough that the mast doesn't flop around, but loose enough that you can rotate the mast to 90 degrees easily.

I've been racing these boats for about 20 years and I don't find them to be overly sensitive to tuning. I rig mine the same way every time regardless of wind conditions. Your main tools are mainsheet, traveller, and downhaul. Make sure they work efficiently and you're in good shape. Having a good set of rudders and a balanced helm is also critical.

sm