JV,
This post is getting a bit old, but you may still be looking for thoughts. I have sailed for several years with an asym on my Sabre 34, and now for this summer on our new-to-us Saga 43 -- boats that braket your size. Some thoughts we've learned.
* Asym spinnaker sheets need to be measured, but they are roughly 180% of the boat length, give or take a little bit. On your boat, you'll need at least 70' per side.
* Line size is 100% driven by handling and winches -- anything big enough to work in the winches is overkill for strength. So far this summer, using lines I have around, I've been using a piece of 1/4" dacron on the Saga 43 and it has been fine in true winds to the teens. But it WILL be replaced!
* On the Sabre, I made sheets, and will for the Saga. I used 6mm dyneema, breaking strength around 7000 pounds and it floats. I "fattened" it (opposite of stripping) for about 15' of the 65' sheet. The rest of the sheet is either going to the spinnaker (about 10-15') or the huge tail that you just pull on to pull the sail around. The working part is really very short. (So, the line is 10' of bare, 15' of thickened, and 40' of bare, going by memory). Use a scrap sheet and test and mark the part that actually goes on the winch. I fattened it by working a piece of 1/8" line inside the dyneema, and then put a polyester cover outside it, getting it large enough to work in my self tailers. The cover used to available from APS before they stoppeed selling sailing equipment -- I have no idea where to get it now. A pair of coiled sheets is smaller and lighter than a single bow line!
* I attached my sheets with a soft shackle -- fun to make and easy to use.
* After fighting outside gybes for several years (conventional wisdom!), I tried inside and have never gone back.
* Lots of people talk of taking the tack line aft so you can "adjust it." I cleat it to the bow cleats and never adjust it. Watch racing asyms - J90's, etc -- they NEVER adjust it!
* I run my snuffer line through a block. The block has a short loop on it (1 foot). The loop goes though the bow cleat and over a horn. That way, I raise and lower the snuffer by sitting on the foredeck with the snuffer line between my knees, and pull UP -- the sail will never pull me overboard.
* As others have said, the main is a huge safety factor. G/F and I got a huge wind increase (from 12 or so apparent to low 20's apparent) and while surfing along at crazy speeds, she drove down to 170 degrees and I snuffed it easy peasy. Even in light air, pushing the wind to 170 makes the snuffer easy to pull down.
* As others have said the sail won't work below 170 or so. Your Tartan may be "slippery" like our Saga -- push the true wind around to 150, and the apparent will pull forward to 90 or so -- with that combination, we make boat speeds of 6+ in 7-8 true wind speeds gybing through 60 degrees.
The asym is an easy 2-person sail in winds to 15+ true, and we rarely have a day we don't use it. It's a must have on our boat!
Harry