Fix your Dremel 225 Flex Shaft Attachment with this printed guide and now you can cut along the straight line.

Theoretically with small D38mm saw (original dremel size) it should be possible to cut 5mm thick plate.

This guide works with a truck made of bought piece. Like mrtattoohead suggested in "version 1" it can be now made of a standard profile.
If you want, attached is truck stl file. Model has 10x4x100mm dimensions so scale it in length according to your needs.

Doesn't Matter

Yes

Some may not need supports.. best would be to check yourself.

Printed parts can be screwed together with two M5x25 bolts.
Profile I used as a truck is a steel 10x4mm piece. If you need different dimensions please let me know. I will make a variant of a bottom guide with customized slot for the truck.