It is very positive, if person, who make his first post, is so educated! After some time we can hope to get all problems solved.
I have been spending also lot of my free time to understand at least something and this what I found, I shared with you.
In following I confirm my working set up on Nokia E90 and Mobile XT v 500.50:
gmapbmap - Worldwide Roads Basemap
GMAPSUPP - CN Europe NT 2011.40 (Põhja_Euroopa ja UK)
gmapprom1 - BlueChart Atlantic v9.5 (Atlantic ocean, Indian ocean, North Sea, Baltic sea, Black sea)
gmapprom - E&P (Estonian inland waters Peipsi); Regio Baltic v1.6
GMAPSUP2 - Regio Baltic 1.6
The file gmapprom I got when I joined Est inland waters lake Peipsi and Regio Baltic 1.6 with Gmap tool. I was myself also a bit surprised, that I had one map twice. Would like to say that Regio Baltic under file name GMAPSUP2 did not work when I had same map installed into memory of my sd card under name gmapprom. After that I removed all map files to an other location at my sd card. First I loaded plain inland water map under name GMAPSUPP. I got message, that detailed maps does not support routing. Now I installed under same name the Regio Baltic - no messages...
Now I will look for a map, what could be useful to install under free GMAPSUP2 name, I let you know
If someone believe it to be useful, then please use it for your fun!