Disadvantages of run 650B wheelset on a 29'er
But you don't know your bike would handle any better with 650.  In an earlier post you said you liked your  wife's bike.  Wheel size is not the only difference unless they are otherwise the same bikes.  Put your wife's wheels on your bike and try for yourself.  My 29er is better than my old 26 is every way.

The clearance is only 1/2 the difference so a change of about 2 cm. But 2 cm is enough to notice. Not just clearance you change geometry.  But that may be a good thing for your supertanker.

Also the weight of the wheel and tire will effect the performance.  Even how easily it turns Angular_momentum.  A lighter wheel and tire will be more nimble to turn.   A lighter 29er might give you (a bit) or what you are looking for.  In the end a different frame geometry may be what you need.  I think you are putting too much on wheel size alone.