Will definitely get Allen screws for ease of access.
If you choose stainless, like I did, in theory a little electrolysis is to be expected, but... so far I have not noticed any worrysome development. Not in over 30 years...
About the head gasket. Before the CB500 was launched, you can trust Honda has done a lot of testing. What Honda couldn't well foresee that in practice, bikes would hibernate for months or otherwise be inactive for long periods of time. It's my gut feeling that exactly that is at the root of the notorious sweating or even leaking of oil, that all CB500s and Cb550s will - sooner or later - fall victim of. It's not so much the headgasket, as well the seals in the oil passages. When I bought my bike in 1980, it sweated oil and... it still does today. In the past, two experienced mecs have promised that after their interference, there would be no more leaking. Alas! So, I've learned to live with it and as long as it doesn't dirty my pants, I see no reason to take action. Once a year I clean the engine with a biodegradable degreaser and water and at every tankstop I clean a bit with a paper towel. It's done in a ten seconds, so for me it is no big problem. It
is however for those that want an immaculate jewel like looking engine and polish crankcase- and clutchcovers to a degree in shine, that I have never witnessed when the bikes stood
new in the showroom.