After 24 years of sailing Wildcat, the original main sheet has finally worn out and needs replacing.
I am still using the original fiddler block arrangement (although I've added a fine adjust arrangement).
The specs call for 90 ft of 3/8 line. Has anyone dropped down to 8mm line? What brands of rope are others using?

Samson XLS. 3/8 it was .70/foot halls spars scrap cordage.

http://www.defender.com/product.jsp?path=-1|118|311417|314169|913347&id=36196

If you're purchase has increased from original setup, you're going to need longer line.

I have Harken 383 4:1/8:1 fine tune system for sale if anyone wants it. New in box. I fixed my old problem. Cheapest I found on web was $450 shipped. I'll sell it for $350 and I'll ship for free.

Thank you.
My purchase doesn't increase on the primary system. It is still the original. I have however added a 4 to 1 fine adjust system on the first leg of the original set up; technically then the primary main sheet will decrease in lenght by about 4-5 feet.
I was wondering if I could go to a cordage with less stretch IE T-900 and drop down to a smaller diameter such as 8 or 9 mm. My concern is that if I do that I may end up with a line that kinks up and doesn't run freely through the blocks and as well is harder on the hands.

Russ - we run an 8mm mainsheet and it runs fine. It does make a difference what like you run though. I for the life of me cannot find the invoice to tell you exactly what line we are using but if you call Henry Mallard at LayLine he can look it up and help you get the right stuff.

I've made the case here several times that using high tech line in multi-part purchase is a waste of money and may be less satisfactory than standard Sta-Set double braid. Fully trimmed, you have at least four and typically six parts bearing the mainsheet load over a short span. I could go through the sheet load, line tensile strength, and stretch calculations, but it is simpler to consider what you have in your hand. In 20 knots of wind, you can probably still trim the mainsheet with one hand, so the load on each part is likely less than 100 lbs. Smaller diameter, smooth finish line runs more freely, while larger diameter soft cover line is easier to handle and holds better in the ratchet. If you are still set on spending extra, be careful not to get a line that is stiff or will stiffen up from exposure to UV since the mainsheet spends most of it's life in the sun.

Fully concur with Bob. I tried other stuff and went back to white 3/8" Sta set. It's good on the hands and runs through the blocks well. I also use another color 3/8" Sta set on the fine tune. This old thread shows the picture with larger diameter Regatta Braid - I returned to Sat set and like it better.

Gents,
Thanks for the guidance.
I purchased 95 ft of white Sta Set double braid. The extra length is in case I screw up doing the eys splice and have to have a pro repair my mistake.