I am starting to replace wire rigging with Amsteel where it makes sense. Today I made up new stays that connect the ama (float) bows to the tip of the bowsprit, and keep the sprit from moving laterally. (see image)

Anyway, my question is about whether anyone knows if there is a formula that can predict the amount of length lost to construction "shrinkage"? The loss is related to the diameter of the line increasing for the length of the "bury".

I found that if I measured the line with the Brummel lock complete (before burying the tapered tail) it was exactly the right length, but when the bury was complete I had lost a few inches. My first try was a learning experience (I'll find another use for the line, at some point). My second try I compensated but was still off a little (but it's usable for the intended purpose). Any tips to get it exact?