i dont know who you talked to.......but i was looking into 314 and z shafts awhile back and the place i talked to said they could go out to 31 inches on a 314 and 32 inches on a zshaft......i think it was seyberts.
If deflection is a concern I suggest a 30.5 inch butt with a standard 29 inch shaft. For taller people and deflection, odd sizes are getting more popular.
Tell them to build the butt 29" long, but with a short butt cap. Then, after they send you the cue, buy a new long butt cap (you could even tell them to throw one of theirs in the box) and screw it on yourself. Haha!
Actually I am poking a bit of fun at you because I am really confused at why that 1/2" is posing a problem for you.... Do you measure to the end of the butt cap or the bottom of the bumper? That could be 1/2"....
I actually have an amazing Richard Black for sale that is 59 5/8" long. The price is $3600, but you would be the only kid on the block (or in the world for that matter) with a cue like this: one of a kind, retail value: $5k with documentation). Let me know if you want photos. Richard's cues hit like a dream.
Perhaps because Predator doesn't make their own butts. Just buy the butt from another place and get a 30" Pred shaft to it. Or even as Mr. Webb suggested on getting a 30.5" butt with a regular sized 29" Pred. shaft to it.