My wife ordered the C4 ladder for me at the end of November, it arrived earlier this week. I installed it today with no issues on my 2020 TRDP. I read through the PDF instructions on the C4 site, watched the C4 install video, and also read through the install guide on Trail4Runner.com. The C4 install video says to measure 9.25" for the bottom bracket measurement, the Trail4Runner site said 9.5", I went closer to 9.25". I did a couple test fits before removing the top bracket adhesive covering. I stuck with what the C4 video said about how to initially place the top bracket (pretty much centered so that the washer covers the entire hole. I was a little concerned that the top bracket wouldn't sit flat, but I thought after tightening down the bottom bolts that it would sit flat, and it did. Seems like a solid product, it doesn't move at all when climbing it or pulling on it.