Stijn,
I don't know how Explosia is, but American powder companies have knowledgeable test experts on site to help the handloader. It would be worth your time to give Explosia a call or drop them an email. This could be a problem if they only speak Czechoslovakian, but since their guide is in English, you may get lucky.
The Reloading Bench portion of the 1911 forum has many members more qualified than me that also may be able to help you.
http://forums.1911forum.com/forumdisplay.php?f=58
It looks like you have a good understanding of pressure and velocity, but the rule of thumb I've always heard was to begin 10% lower than the recommended load and then work up. Better to be safe than sorry. Some people like shooting hot loads, but I have always enjoyed light loads so would start light and work my way up. Do you have a chronograph? It will be a useful tool for accurately measuring the velocity of your rounds.
Also, I've been using Dillon equipment for 20 years and they have the most outstanding customer support service I've ever had the pleasure of working with. I've called a few times to ask for help and it has always been a positive experience -- the last time they sent me some new parts for free.
Be Safe,
Dennis