I am sure this has been discussed on the forum previously, but I think we all agree the standard method of attaching the brake drums to the hubs is a bit of a pain, especially if you have the 10 hole variety, so Marcus taps and helicoils the hub (I believe) but with that method you cannot avoid not having the standard non turning bolt heads, whether that be eccentric bolt heads or filed down hexagons, I have seen both, are they both standard factory fitments?
But if you are prepared to lose the non turning bolt head, I think Marcus uses socket cap heads, why not simply use a socket cap head long enough to put a nylock nut in the normal position, you would only have to engage and hold a stationary spanner whilst tightening the bolt with an allen key, I think the last time this was discussed two concerns were raised, 1, was the weight gain of 5-10 nuts, I discount that on a road bike, 2, was whether the socket head cap bolts were of sufficient strength to be used for this application, I don't know enough (or anything for that matter) about metallurgy to offer an opinion, but presumedly Marcus does know enough, and has done some pretty high mileages, but I don't know how many of those mileages have been done with his modified hubs.