Ouch! I've attached a few K stand mounting plates (just did one for my city bike yet to be painted) and one thing I do is to braze on an axle spacer onto the plate where the mounting bolt hole is. This allows the K stand to be very tightly clamped but have none of that force acting on the stays. There's no top plate and with a tall enough spacer access to the bolt head is still good. The other thing I do is to braze on little posts that will cradle the K stand body and prevent it from rotating (due to the swing of the leg). Glad to see you fixing up the bike. Andy.