How to measure and cut leather for prod

I am building a crossbow with an aluminum prod. How do I measure to make sure the leather fits the prod with enough room to stretch it on?  Is there a best way to sew/lace it on?

Hey hello and welcome to the forum, don't really understand your question dude.

Measuring an aluminum prod for leather cover:  First of all, I always use very thin leather: preferably goatskin rawhide or calf rawhide. I make the cover in two pieces: one for each side and join it in the middle.  Measure the distance all the way around the prod at the center (where these individual pieces will start) about the middle of each limb and around the ends, just inside the nocks. Make yourself a paper pattern, use that to mark and cut two pieces of leather. Punch a row of holes along the base of each piece, and along the sides about 4-5 mm in from the edges. 
Now put the leather into warm water to soak for an hour or so.  That makes it pliable.  Being careful to put the inside(rough) surface against the prod, you will stitch each piece of leather a limb of the prod.  YOU WANT THE STITCHING TO RUN AS NEAR AS POSSIBLE DOWN THE INSIDE, CENTER OF EACH LIMB. When both sides are stitched on, run a row of stitches between the two pieces, so they won't slip outward as they dry.  Your leather will shrink a bit as it dries.  If you get it nice and tight, it will look nice.  When the leather has thoroughly dried, paint it with leather dye.  One or two coats should suffice.  When the dye has dried, give the whole prod a spray coat of clear laquer.  That will make your leather cover more weather/humidity resistant.  Note when you're done, the prod will have a seam along the inside surface. That may make it sit a bit crooked in the bow-socket, but you can easily fix that by putting some leather spacers in the socket with room for the seam. 
Have fun.  Geezer.

Thank you for the help. Works great.