The only issue was that the fins are so close to the bolts, you have to use an open end wrench, because a socket won't fit in there. You can still get them tight enough, no problem. With any cover or plug, they only have to be tight enough to stay put and not leak.
Why not swap the bolts for Allen-head fasteners?
I thought about including Allen bolts, but figured it's more common for people to have a wrench/pliers/crescent wrench to remove stock style bolts if they ever need to service the valves in the field.
You know, I think it would look a lot better with some nice shiny Allen head bolts, anyway. Adds to the bling, even if you rarely see it. You could include them, or offer them as an option, perhaps.
If anybody can tell me the size bolts to get, I'd appreciate it. I'm going to go buy some tools soon, so I'll try to get what will fit, too.
Anyway, I really like the pieces, in any case.