I don't run on-board glow drivers on my inverted 4-strokes, just an extension to the glow plug so it's easier to hook up the power panel igniter (Sonic Tronics makes a nice one, Sullivan will not work with short anode plugs). I usually mount them to the firewall with an access hole in the side of the cowling to stick the igniter through. On the Cub, you could actually mount the hook-up on the top of the cowl sticking out in the location the fuel indicater would be on a full size cub.
If you run good glow plug (OS "F" or YS) and tune your low speed needle carefully, you should be able to get nice reliable idle of 2K with good transition even without on-board glow. Of course on a Cub, you can easily support the added weight of an on-board glow, and it makes it even more convenient to start (switch on, flip prop, & go!). You could get your idle a little lower with on-board glow as well, which is pretty cool while on the tarmac.