Interesting Doug, is this something that won't work with am I1pro1 because of hardware limitations? I've got the publlish software, and a couple (750, and 10000xl) of epson scanners, that it would be great to take to the next level.
Will this work with the trial of Patchtool?
It should be possible with patch tool. You can extract the RGB values from a scanned chart. I don't know if Patchtool can combine the RGB CGATs and the spectro CGATs Lab values or if you would need to do that in Excel or something similar.
I have developed a program that reads in one or more scanned charts, extracts clean RGB data, and combines them with the spectro CGATs file to produce an RGBLAB CGATs file that works nicely with Argyll. I haven't put it on github yet but expect to do so shortly. It's designed to work with either I1Pro2 targets or I1iSis targets. I haven't tested it with I1Pro1 targets.
For best results (dE averages well under 1) you should also use a program that removes wide area crosstalk. Otherwise there's intrinsic error, sometimes quite large, due to this crosstalk that can't be corrected with a profile. I believe the 750 has a similar characteristic crosstalk to the 850 that I use. I've posted some info on this in this forum and a link to a github program that does a good job fixing this.