1. the screw size/type depends on what cleats/fairleads you get, and for Harken products are clearly labeled on the back of the package. I think the micro cleats are #8 machine screws, and the standard size cleats are #10 machine screws. whether you need "Pan head" or "oval head" and the length depend on which fairlead you use.
2. To install you really should tap a threaded hole for your fastener (taps and tap drills are available from http://www.mcmaster.com/
, among other places. Then use "Tef-Gel" on the screws (isolate the SS screw from the aluminum crossbar) and just screw it all together.
For what its worth, I have a slightly different setup that Pelican's that seems to work well for me- I have a Harken H470 "Micro Cam Cleat w/X-Treme Angle Fairlead". its mounted a little bit behind the centerline of the crossbar, so the furling line tends to stay in the cam cleat without the forward fairlead like pelican uses. I then use 2mm "Marlow Excel Racing" line for the furling line.
I'll take some pictures this weekend if this isn't clear to you.http://www.apsltd.com/c-7008-harken-micro-cam-cleat-kits.aspxhttp://www.apsltd.com/c-7269-small-diameter-high-tech-double-braids.aspx