I've got a double rail frame built with 1.9" OD aluminum pipe- I am told it is 1.5 IPS ASTM B429 (6061-T6XX extruded structural) with an 1/8" wall. It's thinner/lighter than Sch. 40 1.5"/1.9" OD pipe. My frame builder set the inner frame rail width to be the same width as the inside of the tubes, so the inner frame rail does not rest on the tubes.
In playing some more games with frames, I noticed that my inner frame rail is sagging about 1/2" or so (see red rails on attached image). I carry a couple coolers and a drybox so it's got some load on it, but I was surprised nonetheless. Is this amount of sag worth worrying about?
If yes, I've thought of a couple potential solutions cooked up:
1) swap out the existing rails and replace with the thicker wall sch. 40 aluminum pipe, or
2) change the configuration to have a partial double rail frame (see example frame in picture on right), so it's got more cross rails resting on and supported by the tubes.
Any thoughts on which way I should go?