Thanks Doug. Two followups;

What to make the spacer of? Are there commercial products available or
are we talking about cutting a chunk of rubber to fit? Are we talking a
bronze dougnut?

NPS threading on the through-hull and the seacock; what to seal with?
Pipe dope or teflon tape? I think I read teflon tape only for tapered
threads so.. ?

Thanks again,

-CB