Hiya mate, whatever the tips on the structure I would say DONT DO IT. The top box is the worst possible place to carry stuff on a bike as it is well back and high up!!. You make the bike instable with weight in the box as well as dangerous to cross winds. Fit side boxes if you need to carry weight, NOT top box. Good luck!!!

__________________
(Now sold on, sob) 2011 Blue XT660X with gold wheels, was 26,500 km.
Engine mods: K&N Stage 1 filter, DNA Stage 2 filter, snorkel removed, Kev fuel mod fitted.
Plus: smoked Puig screen, Yam aluminium sump guard, Yamaha / Acerbis handguards, Givi Trekker aluminium side cases, Leo Vince X3 cans plus Kev front fork mod and Fender Xtender. Just fitted Michelin Road Pilot 3 tyres.

SOLD the XTX for a Super Ten 1200. And just bought a Raptor 700 so staying on here for some tips....