The test is completed...and the winner is
This comes is various sizes but I got this one so I'd have enough to hold up 30 boards. As I tested it, I cut small (about 1/2" squares) and it worked perfectly, held tight and come off with a slight amount of pressure but won't come off my mistake. I also removed the sticky sides from the art board and the backer board without any problems. It was solidly attached to the art board and I was able to roll it off with pressure from my fingers and on the painted plywood surface I inserted a thin sharp knife blade to loosen the corner and grabbed it with pliers and peeled it off easily without any damage or residue on any surfaces. It is not thin, but I like the look of the small shadow that is created because it stands off the backer board slightly.
#1, Velcro Clear Transparent clear coins. These are thin and I have used them on smaller art panels with great success. Perhaps because this mounting board was warped, it came loose on one corner, understandable, but since this job depends on a perfect presentation, I didn't want to jeopardize the project.
#3 Command Picture & Frame Hanging Strips. This is rated for 18x24" frames and up to 12 lbs. I chose to use only one piece in the center top because of the weight (for the test) and it worked perfectly fine and came off easily following the directions, but would stay firmly attached otherwise. It kind of snaps together and the directions to apply it are a little time consuming. I mainly decided not to use it for this job because lining it up to hang level and straight, etc. is not as easy as the velcro. If 2 strips were used, one on each side at the tops, it would probably line up quicker and easier. These strips are excellent for being easy to remove and leave no residue or damage to either surface.
#4. Silicone. I used three small dobs about 1/4 teaspoon along the top edge and clamped it. It was very firmly attached. After 2 days I couldn't remove it by pulling it (like opening a door) from the bottom edge. One spot (with the least amount of silicone) did come off, leaving residue on both surfaces. The second and third spots tore material from the painting panel which remained attached to the painted plywood mounting board. I purchased Goo Gone and have not yet attempted to remove the remainer of the torn materials from the plywood base.
#5. Scotch Super 77 multi-purpose adhesive. I had high hopes for this product but decided not to test it this time because of ventilation. It is highly flammable and states that even pilot flames are a risk. So because it's freezing outside, I will wait for better weather to use this project. According to Blick, it will work very well and I'm sure that I will give it a chance at a later date.