All of the square tube will be 1.5". IIRC Ron said that it's 1/4" wall thickness so that's why I said that we are still well within the realm of 'designed by Max Headroom'. The receiver tube itself will of course NOT be 1.5".
Basically, to keep it all behind the cladding, the 2" tube will not fit without some very creative engineering/fabrication. The $$$ just don't make that practical (don't want to design something that nobody can afford). Besides, that creative fabrication would almost certainly have as much effect on structural integrity as switching to 1.5".
The problem lies with the curvature of the cladding and the location of the fuel tank shield. 2" stock could also be used if the fuel tank shield were modified but then it wouldn't be a bolt on modification. Again, designing something that couldn't be bolted on in the driveway was NOT an option (not everyone can drive from Azrizony to North Darkarta for a custom Ldub install).