It's been a few years since I've done any crewing, but for comfort and support I'd either go for an adjustable harness with thigh straps (rather then a single crutch strap), or a custom made job..

As for tips, here's a few general things.

- I replaced handles on the trapeze wires with a plastic disc (big enough to support the bottom of your closed fist) and about 400mm of 6mm rope above the disc. It's heaps easier to grab the rope rather than a handle when you're going wire to wire.

- Keep the handle (or disc) nice and high, but still within easy reach. This means you can get out on trapeze nice and early.

- keep legs bent in the choppy stuff

Are there any specific areas that you're finding challenging?

If your new at it I would keep your trap adjusted high because it makes it so much easier to get in and out. I have purchased a magic marine racing harness and it is sensational. It has infinite adjustments and when it is right it is great.
Also keep something in your hand to help keep you attached to the boat. You dont need it but it is a bit of a security blanket. And lets face it you should ahve somthing out on te wire with you anyway (kite sheet/main sheet/jib sheet)