Water pickups and Seacocks

[Billybob]

I want to put one of those bronze thru hull strainer pickups in my boat bottom for the washdown/livewell.The pickup is threaded like a plain thruhull,but it also has screw holes around the flange.The seacocks are the same deal, female pipe thread plus 3 or 4 screwholes in the flange.What is the proper way to do this? Would seem to me I could just drill the 1 hole, bed the pickup with 5200 and tighten down on the locknut just like a regular thruhull.But then whats the point of the flange on the seacock, why not just use a regular ball valve?Even if the hole pattern of the pickup and seacock matched, you can be sure that they wouldn't be aligned when you screwed the cock on tight.So, what do you guys do?
Bill