Does that leave enough of a head? SHCS heads are pretty small to begin with. If you're satisfied though, it is a nice shortcut to making model bolts. Note that scale head size should be about 1.5 times the bolt diameter, if you're concerned about such things.
One suggestion: use fine threads. I assume it's too late now, but fine threads are closer to scale. Consider a 1"-8 bolt. Scaled down to quarter side, it should be 1/4"-32.