The use of the screw-attached plexi mitigates your fear of marring the pedal with adhesive. This technique is also very effective on wah or other large format pedals. Mission even sells kits for their pedals with plexiglass and larger screws.
I got a large piece, 2 x 4 feet at the hardware store for just a few bucks. cutting it out takes literally 30 seconds.
I used this on my prized BK butler pedal – I did not want his autograph on the bottom being marred by the adhesive; this way I can still read the bottom, and have a place to attach the velcro in a non-destructive manner.