Crank and BB question

See, I knew it was a stupid question! :)
Thanks again.

Moving to the inner ring position shifts the chainline inboard by about 6-7mm, and with no possibilty of moving it back out by using a longer BB spindle. No hubs are that narrow. Also, you'd need to fabricate a spacer for the hidden bolt, similar to the one which is usually sandwiched beteen the rings on the stock set up but longer to take account of the absence of the outer ring. Oh, and if you use a ring much over 42, especially on a track frame with no dimple or curve in the chainstay, it will hit the chainstay.