PP + Profiling Canvas for aftermarket ink on Epson 10600UC

Hi,
When I import my color target and PP pattern printed on canvas and scanned on HP5400C using the recommended settings (300dpi, 0-255 exp, 75% saturation - gamma setting seems not available though) around 200-240 blocks are at maximum brightness (red x). The color target pattern imports to PP with no errors and everything good from the same scan. The histogram shows good but with the right side cropped short of the bottom line.

The entire top row of the PP pattern on the canvas has red x, plus some other bright boxes.
The resulting profile is light on yellow and red and saturation of all.

I'm wondering if this is due to the texture of the canvas interfering via light diffusion during the scan?
Is it possible that a more accurate PP ICC profile could be obtained from the after market ink using photo-paper for the pattern, and then editing that profile, if needed, after using it to print the test (digital dog image) on the intended canvas?

If not, can you advise any other solution - or other settings on HP5400 (using HP Precision scan 3.1) that might help lower the max brightness X count on the canvas to result in a better color and saturation profile.

best regards - PP is good SOLID software!

cheers :-) ;-)

ps I think I have this sorted now, i.e. restart Photoshop to apply new printer driver ICC profile & use identical media to that profiled. The pattern squares showing as max brightness make little difference to the generated ICC profile obviously.

Update - I'm getting there via PP icc profile edits and test prints. The initial profile was low on cyan and the saturation was low. I am wondering if the fact that PP recommends setting the HP scanner to 75% saturation, results in a better PP profile - but is that profile made then 25% low on saturation?? As that is what crossed my mind here. So printer is now running test print with icc saturation increased 20%. PP version is an old v.6.03

cheers to all - it works - one at least gets a good feeling of control when its so easy to edit the icc!! :-)