Good information, thanks, Ed. @Bob, the dimension (41" behind stem head) in the drawing I received from Allen is a good bit further forward than the V-berth bulkhead. If i had to guess, the V-berth bulkhead is probably closer to 55" back from the stem head. It's all moot for me, my 40 doesn't have a forward anchor locker, or a bulkhead separating the v-birth, i'll be installing something close to what's depicted in the drawing.
For anyone who has an inner stay on any of the J/4x's, what type of sail are you flying off of it, and how did/do you handle sheeting it? Storm jib is obvious (?), but likely/hopefully won't see much use. My primary goal with an inner stay is to add another gear for upwind work, especially offshore, similar to how a solent rig would be used. If it works out to add horsepower reaching in lighter conditions, great, but my plan is a 'blade-like' headsail at ~95% of the inner stay foretriangle.