help on making a wooden Xbow prod

[Thesquirrelslinger]

I know the requirements for an xbow prod are slightly different than a normal bow.
1. it has to stay at full draw for a signifigant amount of time without losing power.
2. it is drawn about half as far as a bow. 
3. i would like it to be about 45' for a 15" draw.
4. Does the high weight(near #100 hopefully or higher) make a big difference in design?

i am thinking a bow 3 times the length of the arrow, red oak maybe, or maybe BL....
how wide? wider than normal cause its going to sit at full draw?

[adb]

I've made a couple of xbow prods out of yew. Rawhide backed. 36" long. The power stroke is only 8". Last one was 80#.