Hi Todd
Sail hard ,-as Team Castrol used to say ,-during the G T race ,-best of luck in it .
Team Morada did pop off a rear bolt on the crossbeam in this years Tybee 500 ,-it is fairly common on the 6/0 with added larger spin adaptation placing added loads and increasing the racking tortion aspect of 2 hulls working independantly through waves along with the stress of sail loads.--The distance on design of the 6/0 ---originally a 5/8 stretched out to 6/0 meters --from front crossbeam to bow adds to the racking leverage .

I did the same in the 99 W-1000 race ,-popping the rear outside bolt on the 6/0 -then raced with Smyth spin of 450 sq ft ,placing evan larger loads on it ...
The only way we finished the leg with about 40 miles to go was to take the spin down ,-then we used the trap wire and cinched it to the rear foot strap which held the boat together from mast leverage while we babied it in to the leg finish .-It would have been better to the trannsom gudeon --but the foot strap miraculasly held.

The leading active 6/0 racing expert on the6/0 is Rick Bliss at N E CATAMARAN . Rick raced the Tybee 500 last year .I recommend contacting him and asking advise on this and any other aspect of distance racing you may have .

I recall in the early 1000 mile races also a highly modified 6/0 by Smyth ,-he recognized the problem and added a center bolt with reinforcing up through the hull inside the rear beam with a semi-circular washer type fitting with bolt and lock washers over --the interior hull in that area would have to be reinforced as well and loads spread out .

--The only other suggestion I might make is going to the 270 sq ft spin that the I-20 uses .-
It has a more forward block lead placement that takes the pull away from the back beam and helps reduce racking stress caused by larger spin with aft block location .

In the higher winds of the G T race the smaller kite will be more managable and the ability to reach with spin more may be a good trade off with the 270 sq ft spin rather than 348 sq ft aft lead version.

Hope that is helpfull
Carl