In my time reading an old warbow forum I ran across an interesting theory. The theory pertains to the warbows that are percieved to have a draw of close to #180 pounds. The aforementioned warbows were square in the handle cross section, which would make them painful and undesireable to shoot by hand. They also fit into "U" shaped brackets on the gunwhales of the Tudor flagship the Mary Rose. The brackets are spaced about seven feet apart, enought for a longbow. The theory is that these extreme bows were used as mounted crossbows whereas the archer would place the bow in the bracket and use both hands to draw while using the rock of the ship to gain elevation.
An interesting theory no doubt! I've tried researching for pictures of these brackets but haven't come across any yet. This theory is not outof preportions and it would be interesting to see more investigation.
Here is the link to the original forum post. Go near the bottom of the page and look for the name 'glennan' on the left.