Is there a kind soul out there that could measure and tell me the distance aft from the center of the mast step to the center of the shroud mounting points?

I am building a small 19' trimaran and using the rigging and sails from my 16, BUT I sold the hulls to somebody who needed them, and forgot to measure before he took them away! Now I'm trying to figure out where on my akas (beams) to put the shroud mounting hardware.

I'd be most grateful!