Mio Spirit 7670 is a pretty capable device. It can handle a lot of content.
My ancient Prestigio, which has a 300 MHz CPU and 64 MB of RAM, with Primo KIA handled about 500-600 MB of content without any problems.
Unfortunately, maps have grown a lot since the period when WinCE devices were dominant.
Rather, I would say that you made mistakes on the other side.

I don't know which shell you used for unlocking, but each of them can be made "lighter" by removing unnecessary components.

Apart from that, several other things are very important about iGO itself
- only one (or two) language and voice files
- only two licenses for P 2.4, but Primo 2.0 requires only one
- without redundant speedcam files
- no overlapping hnr files
- well adjusted sys file
- light DEM
- Primo (any) does not recognize fjw files, remove them all
- and of course, you will not put the whole of Europe, because it is certainly impossible to go through all the countries

All this is mostly mentioned in the note in the tutorial I posted

Minor tweaking, in the sense that the device's storage memory keeps a smaller region where you mostly travel, and you put an additional one on the card or few that you plug in as needed, also helps.

Have you tried package from [Only registered and activated users can see links. ]?