Does anyone have a good way of securing a speed control (relatively large one) short of velcro. I need to be able to kind of stand it up with minimal area covered so that I can maximize the air flow around it for cooling. I'm putting it in the front section (just aft of the firewall) in the fuselage of a large trainer.

you can leave it dangling in the air as long as the plugs are tight.

If it's in a relatively accessible area, you could use the stick-on zip-tie anchors on the fuselage, then zip-tie the ESC by its power wires. The anchors I'm talking about are available in packs of 8 in the electrical section of Home Depot and other big-box stores.

Thanks much for the help. It's much appreciated.