In channel vent visors do not have this benefit.
In channel window visor problems.
The heat will allow the visors to flex into place.
Obviuosly the first time you put them on and roll up the window it ll be a tight fit but that s what helps them seal.
Also you will need to tug outward on the visor when you roll the window up the first few times or the window will catch on the edge of the visor and possibly break.
Leave the visor in place and do not roll the window down for a few hot days to allow the window with the visor mold into place.
What you should do is take a pair of tin snips and cut the visor in the middle to make it easier to take out of the window frame.
Obviously do this with the windows all the way down.
In both cases no drilling is.
I ve only had in channel visors on my vehicles as i think the outside mounted ones look pretty awful just my opinion but i ve never had any problems with the power windows not operating properly.
In channel vent visors are designed to perfectly fit onto your car windows channels while tape on vent visors require adhesive to fix them on the window frame.
Pull out the pieces and don t worry if the rubber gasket comes out with it because you can clean off the adhesive and pop the gasket back in the channel.