Hey guys. I would just like to comment that a Per Special (dubbed as such because Per has really crazy solutions, for these kind of things), is quite fast as a 12 move case.
Transforming the Per Special case into a Columns case is fine and well. However, consider the chance of solving with an A9.
Note: I am not condoning this approach, I am merely stating the solutions, and the obvious transformations.
URB -> ULF -> DLB is a Per Special
URB -> ULF -> DFL is a Columns case
I can sub-3 R'U2LU2R U2 R'U2L'U2R U2.
The Columns case
Can be solved in numerous ways.
URB -> ULF -> DFL
R2DF2D'R DR'F2RD' R
B2D'L2DB' D'BL2B'D B'
L F2R'F' L2 FRF' L2 F' L'
However, here is a really nice case.
R U2R'U' L2 URU' L2 U' R'
Method of approach for a columns case.
Moving the Lone Corner:
You can move the Lone corner
in the example of URB -> ULF -> DFL
URB is the lone corner,
ULF and DFL are AnI
URB and DFL are polar opps
URB and ULF are interchangeable opps
but you can see that URB isn't next to any other cubie in the cycle so it's the lone corner.
When moving the lone corner, you only want to do a quarter turn setup.
Do not turn the layer, that the lone corner shares with it's interchangeable opposite.
URB -> ULF -> DFL -- Don't turn the U layer.
URB and ULF are interchangeable opposites
Your quarter turn setup with transform the case to where the interchangeable opposites are now either Polar Opposites, or AnI.
URB -> ULF -> DFL
R and B' transforms the relationship between the URB and ULF to twisted polar opposites.
R' and B transforms the relationship between the URB and ULF to Adjacent non-Interchangeable.
Transforming into a Twisted Polar Opposites relationship you will solve with an A9
such as R (U2R'U' L2 URU' L2 U') R'
Transforming the into an AnI relationship, you transformed the case into a cyclic shift. There is a cancellation with the Setup, and cyclic shift, giving you 11 moves.
R2DF2D'R DR'F2RD' R