QTR-Quadtone RIP

I have mixed my own set of carbon-based inks. To calibrate them I only have a cheap 11 step gray target and desktop scanner. I have made a curve that prints and then scans with the same final values as the target. I have done this using a Photoshop curve in the Gray Curve/Curve setting of the Curve Creator and have avoided providing any linearisation data. I thought I would leave the linearisation section in case I ever find someone who can help me take actual density/lightness readings.

The curve matches the target well, but it is way too dark in photos. I have fixed this by setting the Gray Curve/Gamma setting in the Curve Creator to 1.8 (not is the Advanced Adjustments printing section). 

My questions are: Is this the correct way to adjust if the curve is too dark? If I do get density/lightness readings to linearise with, will this process cause QTR to attempt to return my curves to their pre-gamma, too-dark state? How can I linearise a curve with an intended Grey Curve/Gamma setting of 1.8? Am I missing something?

Cheers,
Nigel.