Digital BW, The Print

I use a Kodak DCS Pro SLR/n (13.7 Mp) and  Nikon P7000 (10.1 Mp) both shot in RAW

I edit using a W7 PC with PW Pro and print with QTR.
I convert to monochrome using Transformation, Extract Channel and Transformation, Composite.

I print at A4 on Epson Enhanced Matte using an Epson Stylus Photo 1290 with MIS UT2 inks (I also use the Epson 2100 with QTR and Epson UC inks with Matte Black with equally good results).

I now wish to print monochrome at A3 from the image shot in colour with the P7000 (it's easier to carry round) - obviously the image may be cropped making the file size even smaller.

My question is should I upsample in 48 bit before converting to monochrome ?

Mel