Workflow for Color Slides Using IT8 Targets

I have an Acer Scanwit 2720s film scanner, Vuescan, Photoshop, monitor
calibrated and profiled with Monaco Optix/EZColor, and IT8
transparency targets from Wolf Faust (Velvia, Provia, and Ektachrome).

I primarily scan color slides. My original thought process was to scan
the IT8 targets in 48-bit raw mode and create ICC scanner profiles for
each film using EZColor. Then I could scan my slides in 48-bit raw
mode and assign the appropriate profile to the image in Photoshop,
then convert to the Photoshop working space, Adobe RGB (1998) for
example. The problem I'm having is the gamma of a 48-bit raw file from
Vuescan is only 1.0, so the image is very dark. The image is so dark
that EZColor cannot use it to create an ICC profile. This method works
great using 24-bit raw files (gamma = 2.2).

Is there a better method of creating and using profiles from IT8
targets than raw mode? Should I just save tiffs in Vuescan with color
correction set to none and adjust the brightness to an appropriate
gamma (2.2 for example)?

Shawn Brennan