We have 2 Bim2000s at the Rudder Club, Jacksonville, Florida, and we love them. In light air they are particularly fast to weather, which is 95% of the time here! We have not changed the factory setup. It has the U-shaped lever or "stirrup" downhauling the diamond wires, and the boom attaches over the "hook" on the tip of the stirrup. I attach a D-shackle through the hole in the hook, and run a line from it through a jam cleat to the clew of the main then back down to the jam cleat. One loop, 1:1. This could be doubled by using a double block above on the sail and a single block below for 4/1. When cleated and tied this keeps the same tension all day.
I think going to the mast base would not work.

see boat pix at www.rudderclub.com ...on the multihull page