As Mark says, nothing wrong with trying. I personally just use the Auto settings for the paper type and am getting very pleasing colors. (shadows might be a bit dark)
If the legacy paper is something like a luster or semi-matte, I read that there are all formulated quite similarly. You could therefore try profiles for Canon papers, or even profiles from Breathing color or other paper manufactures for similar types. I did this when trying to find a profile for metallic papers and ended up just trying all the different profiles available for several of the different versions of the paper from different vendors.
With matte papers, since the ink absorbs, I think it gets a little more tricky. This is all just a hunch, and someone who actually makes profiles could comment more, but this is my feeling.
Nothing wrong with trying different profiles though and comparing.
I use Epson papers exclusively on my iPF6400. The Epson line of papers are very easy to get and have rebates all the time, so its a no brainer. The only thing I did get a custom profile for was the Epson Matte Canvas after I coated it with Timeless from BC. No way to take shortcuts here. I'm even shocked they make profiles available for Canvas when you consider that is has to be coated and this really changes the final colors.
