Rob, why not leave a 3 to 4 mm wide annular ring around each bolt hole and stop the worry?
Aside from possible warpage, I do not think the reduced clamp area will hurt the head, but I am hesitant to put 0.005" wire on the head side.
Slick
I agree with your concern about the wire damaging the head - in part driving my interest in this style.
My hesitation for putting rings around bolts/studs is to minimise them robbing pressure from where its really needed.
The picture below, from the article, shows the 700cc RE acid etched gasket - you'll note it doesn't have the rings around fasteners and it apparently was running this way for many years.
The previous owner etched his own gasket as, apparently, these machines are notorious for head gasket leaks (unlike Norton twins - hey?).
The current owner (article author) made the cut gasket but doesn't explain his rationale for adding the fastener rings to the original design.
I have thought on your concerns however and offer the following revision for comment:
Some thoughts on this are:
1. Fasteners 3, 4, 5, 6, 9 & 10 all grip the head alloy and are now about 50% supported by the wider 7mm rings.
2. Studs 2, 7 & 8 all grip the cast iron barrel so should not see fluctuations in tension due to thermal effects. Are the proximity of the rings good enough? Especially for #2!
3. Bolt #1 is a quandary for me - to some extent this one does the most sealing work of any fastener (see shaded area) other than maybe #2. I have added a "bridge" between pushrod tunnels but is that enough?
The head alloy is 25mm thick here with finning and pushrod tunnels quite close-by. You'll note I haven't hatched all the way to the hole here - demonstrating my uncertainty!
4. When I have some masking agent (awaiting postage) I will experiment to see how much control I have over etching - can I etch to 0.005"?
The etching fluid I intend to use is 2 parts hydrogen peroxide (3%) and 1 part pool acid.
5. When I have settled on a design and completed etching I'll the assess risk of using it - 650ss heads are pretty rare these days! (opening Ken??)
I'll keep you guys informed
Cheers
Rob