For the RV-8 it's CS4-3. Vans is the only place to get them, but they are so cheap why would you look somewhere else?
When you need to get the floor up, drill them out and rivet it back in when you are done cleaning it out and installing new antennae etc.
You can put in the extra work, but Van probably got this part right.

__________________
Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is
nothing-absolute nothing-half so much worth doing as simply messing around with
Aeroplanes
(with apologies to Ratty)
2019