I would like to upgrade the kicker system on China Crisis N3223 which I am currently giving a total overhaul(see CVRDA facebook). I have two Selden/proctor wire blocks and Harken block is there a guide re wire lengths?
I think that the simple answer is no as there are two many variables.
You will want the top block as close to the boom as possible so that you can maximise travel. I would make out of splicing ropes - they should be fine with wire blocks - set up tying bowlines where you see fit and then adjust and finally splice, remembering that there will be a little stretch. You will need to sail in both light (with mast upright) and windy conditions (mast raked) to understand the range of travel that you need.
A standard measurement for the take of point is 600mm along the boom from the back of the mast.
John
The block that is attached to the boom has the highest load. Ensure that it is a high load one or otherwise strong enough. 3mm Dyneema will be strong enough when spliced. I would make a trial fit out with ordinary string to find the lengths that are required.