You could also try putting an eyelet fitting on the yellow wire and attaching the eyelet to the glovebox door switch. That is if your car has one (it should I think). With a simple multimeter you can find which leg of the switch is always hot, that's the leg to put the eye on.
I needed constant power for memory on the stereo I put in the 108, and didn't want to tie in to the fuse ends (read - wrapped around the hot side of a fuse post like the PO did). I checked both legs of the glovebox switch and found that the botton leg was alway hot. The memory wire was just long enough to route to the switch. Works perfectly.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.