I might not have totally understood your question - are you laminating lengthwise which will add a backstripe down the neck, ala Hoffman
or are you adding to the stack height of the heel itself? I see the backstripe a lot and think it can be very nice, but I haven't seen different woods laminated in the stack. Why can't you just buy some more mahogany and keep the color and grain looking the same (I happen to have a few pieces of scrap neck blank wood if that would help).
I would guess that you will do the rough shaping with a band saw, then the final work with chisels and maybe a spoke shave. You'll feel the transition from the softer mahogany to the rose (and probably the glue line too) but as long as your tools are scary sharp and you make the cuts at a slight angle to the transition I would think that it would be fine.
I've only built one classical but I rather enjoyed the Spanish heel and working on a solera. Share some pictures here as you progress.