Doug Schroeder Method, Double ic

Correct, larger gauge won’t get you what you are looking for. I tried a standard 12 gauge set vs the DS method with 16ga and the DS method with 16 gauge was certainly better in every way. 

So "one 'test' makes the rule" seems a bit quick to judgement there. When a bunch of folks try the smaller gauge dual cables vs one larger gauge. Plus did you  try two sets of wires 16 g with one pair of RCA? And most important, were the insulation of each type the same quality? 
For example Kimber makes the same cable. KS1111/KS1011 and KS1116/KS1016 same wire same ends, just the '6' has multiple pairs of conductors. I believe six vs one pair for the type model ending'1'.(I own several pairs of the '6' model.

I test and make cables daily. It is what I do. Yes, I test all manner of gauge, dialectic, twist, materials etc.., No, not just once or one combo.

It may be possible to find an outlier to my comment and in audio one must always leave the door of possibility open. I also know we all hear differently. My comment is based on my experiences, in general, with ICs. I did not take the time to post all my gauge testing in my post above.

Yes, the previous posts are in agreement with your comment about additional conductors being a good thing. This is a point of agreement. This is especially true when done in the DS arrangement.  However, if using only one positive and one negative individually insulated wire there is a point when the thicker gauge is no longer a benifit.  It actually becomes a sonic negative. I gave one example. 

Shotgun speaker cables has been around since the 1970’s. That’s not what the SM is about. If one wants to double up speaker cables, then have at it. Enjoy the SQ benefits!