I arranged the group purchase for the new rub rail inserts last year and just yesterday began to install mine. I knew it was not going to be fun or easy, but it went extremely slowly, I was only able to get about one or two inches installed per minute,less considering time to straighten my back out every few minutes ,working on my knees bent over . You need to compress and push down the lower lip to get it under the inside lip of the rub rail,even with soapy water it does not go in easily. Seeing that at this rate it was going to take several days ,I cut about half of the lower lip off the insert to see how that went. Using sharp, short kitchen scissors I cut off between 1/4 -5/16 of the lower lip. This made it very easy to install ,I went from 1inch/minute to 1 foot/minute and it went from hard to easy. The insert still snaps in and is not easy to pull out .I used a 1" chisel to push the lip down and in , I blunted the edge ,grounding down the chisel on a belt sander.
If I were to order these inserts again ,I would have the lower lip reduced by half.
I just wanted to put this out for those that purchased the inserts,and have yet to tackle the job. My boat is on the hard so I moved onto scaffolding ,which also made it easier on the knees and back. The new white insert fit very well and look much better that the old brown ones, a good upgrade !
Hope this helps,