Jessica61624 said:
I would have no issue using it with a Britax seat. However I'd install it without it to get a feel for the install without the Matt. Iirc they mentioned it on the blog as one of the better matts.
This. Britax has crash-tested these mats with their seats, so I would be totally fine with it myself
Although, what I would advise would be to install it properly (following manual, less than one inch of movement at the belt path side-to-side and front-to-back) WITHOUT the mat, put a chalk mark on the LATCH strap/seat belt at a point that you would be able to measure from looking (I.e where the belt/LATCH strap bends into the plastic of the belt path) so that you when you install it WITH the mat, you can get it back to that mark at the point you measured, so you know you aren't getting a false sense of tightness due to the presence of the mat. Hopefully that makes some sense! Great question
I'm sure many others have that question also, so it was a great one to ask!