I'm sure you have seen this post - https://www.crossfireforum.org/forum...ing-plate.html - and the o-ring size that the Original Poster used is a #011 (5/16" ID x 1/16") as listed in post #13.

As far as not getting the sealer in the right place - are you following the factory "channel" on the panel?
Here is a pic of my panel with the Moretite applied to it. Does that look familiar to what you are doing?

RL