I just pulled off my right lower cowl to take a look at what you did. A couple of observations: the mid cowl has a recess, or a cut back area, where the vent is. So putting a cover here, it appears it would also have to have a lip on it, or bend it so that it also covers that cutout, to be effective. Looking at your pic again, it appears your cover also allows for the cutout in the mid cowl.
The other thing I noticed is with this vent covered up, now possibly more heat will be vented out the bottom of the tip over wing cover. Not sure, but it would make sense.
It's very interesting you reduced the heat on your right foot by 75%, that is a LOT. I would be interested in seeing the backside for how you bent it and attached it. Can you tell if the heat out or around the tip over wing cover is the same, more, or less?