Just some history regarding air deflectors for the around the forks area. The airflow coming up from the gap by the fork tubes was identified back in 2000 and possibly eariler as a major contributor to buffeting. The Honda ST1100 suffered from buffeting even though it had airflow holes built into the windscreen. Testing revealed that by blocking some of the air coming up by the fork tubes the buffeting decreased markedly but there was a subtle but annoying side effect, low pressure behind the windscreen. Some of us blocked only a small area while others blocked as much as possible.
At first it wasn't noticeable and the less buffeting was so welcome it was overlooked. After a while though, complaints about the low pressure area surfaced. The effect was very minor but the longer you rode the bike with the deflector in place the more you noticed this low pressure effect. It felt like a slight amount of pressure was pushing you from behind right at shoulder height. There wasn't really any pressure at all, what was happening was that the airflow coming up by the fork tubes was gone and thus less air pressure was pushing against your upper torso. On short rides it wasn't much of a problem and for commuting the reduced buffeting was a decent trade-off but for longer distance riders, the deflectors soon found their way in the experiment bin.
The other effect we noticed was that you started having this feeling like you changed altitude rapidly, a sort of clogged ears thing. When the air flow from in front of your body and helmet is eliminated the buffeting goes away but you also create that low pressure area right where it doesn't need to be.
In the end many of us that went the route of the deflector also went back to the way of adjusting the angle of the windscreen and allowing adjustable airflow to come up on the inside of the windscreen. Craig Vetter did a lot of testing to reduce buffeting and that is why he started putting in adjustable windscreen vents in the Windjammer fairing screens. Since then, Honda followed suit although not with adjustable vents but just holes.
Nowadays with adjustable windscreens, changing the angle of attack can practically eliminate buffeting although often buffeting is caused as much by your helmet as anything else.
There was one additional effect from the deflectors, they stopped the air flow so well that engine temperatures increased in some conditions. By preventing or reducing much of the airflow riding by the fork tubes heat didn't dissipate as was the original intent and a build-up of hot air became a self generating problem. At higher speeds it wasn't an issue but at speeds up to 50 mph it sure was. You didn't feel it but the engine and everything forward and below the rider sure did. Without a place for the heat to go the temps rise, not enough to bother the rider but it can be quite a bit for all the plastics, the fuel tank and associated components.
Just blocking airflow instead of redirecting it can have unintended consequences over a longer term. The airflow, especially up front by the radiator needs some place to go and one of those places is up by the fork tubes. Unlike most cars, there isn't some free space behind the radiator for the air to go so air flowing up by the forks keeps it moving. Once hot air gets trapped in a static area cooling is affected.
We tested the air temps before and after the deflectors were put on and the differences were not small, often 15 or more degree. Factor in a hot day, slower riding or stopped traffic and it can make a bug difference. Heat rises and when it can't it just builds up. You'd think that with some gap not covered it shouldn't matter but measure it and see for yourself. While I haven't testing it on the VFR-X as I don't experience buffeting and it is no ST1100, maybe someone could give it a go?