SIH,
I have the voyager pro billet protector and bar mount sitting here as well, so I could do the same. Though pricey, I'm a big proponent of using Trail Tech's billet protectors because I've smashed a gauge before (abrupt stop slamming my chest into the gauge) and smashed one. That was smaller non-pro voyager. When I bought the replacement head unit, I also bought the protector and that worked great all last year.
Other than loosing the ability to mount things on the crossplate you cut out, doesn't seem like any downside. On your C3 heated bars, which fittings do you have up on the bar? The smaller simple 90 degree fittings or the 90 degree on/off valve fitting? I have the bulkier 90 on/off valve fittings up by the bars so just making sure their is room with those rather than the slimmer plain 90 degree fittings. Could you attach a couple images? Interested to see exactly where it sits all mounted up. Thanks.
I did see that C3 is working on a Voyager Pro specific mount, but it's not ready yet. Not sure how it will differ from the C3 panel mount that GKR posted above. C3's page says the Voyager Pro specific mount likely won't be ready until Jan/Feb 2020; I assume they mean Jan/Feb 2021 and I hoped to have a solution in place by then.
Here is the trail tech mount that SIH is talking about. There are two version. One with handlebar mount and one with RAM mount. This protector could be mounted without the handlebar clamp and instead, mounted directly to a C3 panel mount, like GKR did minus the protector, or it could be mounted directly to a plate mount fashioned from plate aluminum. But I do like the idea of simple is better and mounting directly to the bars for easier removal when needed and easier angle adjustment to get it just right.
Pics (from the C3 website) of the C3 switch mount that GKR used: