The extra twist shouldn't hurt anything, if you want the carbon barrel go for it, but the fluted steel barrel would likely be lighter. According to lilja's calculator, you wpuld loose about 8 oz or so from strait fluting, probably slightly more from spiral fluting, so you would be at 48 oz or so, then have your smith cut the shank back to where only 1" of shank is in front of the action, and finish at 22", and you will be significantly lighter with the steel barrel.
Where you save weight with carbon barrels the most is of you go heavy contour. A steel barrel with a .900" muzzle is significantly heavier than a same contour carbon barrel, obviously. But you will always be able to go lighter with a slim contour steel barrel.
Another option for carbon barrels , if that's what you really want, is look at carbon six or hells canyon armory, both can get the twist/contour you want.