I am building a 4x7 trailer to haul my motorcycle. Construction shown in the photo is 3x3 aluminum and 2x3 aluminum. All aluminum is 1/8" thick and I believe it is 6061-T5. The photo shows 1/2 inch bolts connecting 2x3 cross members and 5/8 inch bolts connecting the 2200 lb torsion axle. When I tighten the bolts, they never seem to get tight. I'm concerned that I could easily overtighten and damage the aluminum. I'm planning to thread-lock all of the nuts, but I need to know how tight they need to be. Can anyone suggest how tight these bolts should be? For example: Option 1 - just snug, Option 2 - tight with a short 3/8" ratchet, Option 3 - specific torque???, Option 4 - other? Update: After a little more research, I'm going with option 4, bigger washers. I'll be switching the washers out with 2x2 square washers so that the load is distributed better toward the sides of the square tube. In the current configuration, with the bolt force focused on the center of the tube, the bolts are easily crushing the tubes. I'm thinking that with 2x2 square washers, there will be very little flex of the tubes and thus I'll be able to get the bolts plenty tight.