countersink cowl screws

OK, after lots of good advise I went with #8 screws for the top of the cowl.
Next problem is that the cowl is too thin for a #8 countersink. I could build up the cowl along the top. Time consuming to get a nice job. Or I guess just c/sink it and accept oversize holes. Don't like that idea too much.
How have others dealt with this?

If you built it up how did you do it for a good finish/minimum hassle?

Have you considered tinnerman washers?

http://www.aircraftspruce.com/catalog/hapages/stainlesswashers.php

Or you might consider bonding a thin aluminum strip to the cowl into which #8 dimples have been made....

hard to beat the clean lines from a hinge...

consider your decision carefully... the clean lines from a hinge are really hard to beat.

Do yourself a favor..use AN526C's with a nylon washer under the head. The drag difference compared to countersunk heads is minuscule and the fiberglass/paint will hold up a lot longer.

If you must use countersunk screws, embed the tinnermans into the surface. I know they are common but exposed tinnermans look like ****.

the aft part of the cowling really should be thicker if you are going to use screws. Rather then put the glass on the outside of the cowling, build up the bottom surface. To get a proper fit relative to the boot cowling you will need to put a shim under your flange. A bonus for having a thicker edge is that you will not see any bulging between screws and with a bit of work you can get a really nice transition between the cowling and the fuselage.

Better than Tinnerman

Nas1169 washers are like tinnerman washers but better.

Go here http://www.gen-aircraft-hardware.com/store.asp?alternate=NAS1169-8

Look at the blue button Basic Image, I think you will like them.

The thing with Tinnermans is for that type washer to seat properly, you have to machine countersink
the screw holes the same as you would for #8 screws and that is what I did here. After a few years
and primarily for cosmetic reasons, I decided to stop using the Tinnermans altogether.

You can see the impression left by the Tinnermans in the paint around a few of the holes.
In any event, the Tinnerman-less screw holes look more pleasing to my eye
and in fact hold up just fine. I did not modify the stock cowl thickness in any way. YMMV.

Thanks for the suggestions. I've decided to keep the c/s screws and build up the underside of the cowl. The top skin and flange is already riveted on so I'll have to drill out the rivets and add an extra shim between the flange and the skin as Tom mentioned. Shouldn't take too long.
BTW Stephen that's a good looking cowling!