Making two types of connections for one device

I recently got a SpeedyBee, so I can do Betaflight adjustments in the field. Directions say you can power it using a 2s-6s lipo, and most of mine have either xt30 or xt60, so I thought I would solder two connectors to it, as pictured below. Before I plugged in lipo, (NOTE!!! I ONLY plan on using ONE lipo at a time) I started to worry this may not work. Would voltage back flow into the empty xt connector, causing a short, or sag in voltage to the SpeedyBee, causing it a problem? I asked on my local clubs FB page, and most of them seem to think, if using just one battery it shouldn’t be a problem, especially if I made a cap for the unused xt connector. So I guess I am looking for a second opinion before I plug a lipo in and ruin my new toy. Thanks in advance for any advice!

Yes, a cap will do.
OR just make a XT60 to XT30 adaptor.

if you have both just put one lead on, the speedybee will power from a near flat lipo. just always make sure you carry a small lipo to power.
if you must fit both you then need two different size covers which is more faffing around.
do what amduttuhari says and make a adaptor. also if using thiner wires the solder connection will be better.