TSUSH Adjustable Support Block (Spool Holder)

I really liked the compact nature of the TSUSH - The Smaller Ultimate Spool Holder
by Doc_Cleaner (http://www.thingiverse.com/thing:2193891) but it just felt a bit to wobbly when in use, like it was gonna fall over any second.

Originally I created the fixed width version here:
http://www.thingiverse.com/thing:2197363

But figured an adjustable one would ultimately be the most useful.

The screws used are M3 x 6mm and to make things a little easier to print I've created a small bridge a