I think our results are exactly opposite yours. For us the Postermax looks really washed out no matter what we've tried. I didn't have a profile built for it but we did use a stock profile from Magic and it wasn't any better. Just very flat, dull, "soaked in" looking. On the other hand, the Sihl prints really pop, they don't look dull or washed out. For the sihl, we actually use a 720x720 Oracal 3651 profile, 8 pass bidirectional, not super fast but not painfully slow and it prints well. Mimaki JV33 and JV3 by the way.