DSF

Timings are way longer for a 3d press, so your 420 seconds is probably not too long at all. Are you getting constant suction throughout the time (Assuming you have a vacuum press)? I've had some problems doing flat items in a 3d press and saw a video on youtube that used the spare silicon diaphragm folded underneath the item. I have a single flat piece of thicker silicon that I put underneath that helps. I've also tried teflon sheets above and below which tends to help with tape marks a bit in my (limited) experience!
Let us know if you've found a good solution yet

I am not overly happy with the edgings on my chromaluxe as well, they seem to almost bubble along some of the edges, and one one print I did, one can easily just pick and it chips off. However, I read with interest about doing it the opposite way, as in from the bottom up...I am very interested as to why that would make a difference in the result. Thanks.