I'm working on the same sort of setup but my experiementation has been slowed by some serious hull repairs!

I have a crazy dream that if you route the bag under the trampoline and put a turning block on the rear beam, you can continue your dousing line through the turning block, on top and forward on the trampoline, up the mast, to the spin block, and back down to the head of the spinnaker - your dousing line now doubles as your halyard. You get rid of one line and ALL that halyard slack on the tramp with the chute up.

In addition to this setup, if you put the halyard/dousing line through the pole to a 1:2 setup on the spin tack line, out of the pole and THEN up the mast as a halyard = one line for a spin set and take down - and with relatively no slack on the trampoline. I had a dream of this one night and I am pretty sure I've seen it since on a few other cats. Anyone know how well this works?