I'm sorry if these are dumb questions. The original Jabsco 59128-0000 on my 1980 C27 standard layout is shot, and I want to replace it. The rest of the plumbing for the head is sound (newer) and properly installed. I have looked at the Jabsco 29090-2000, the Wilcox Headmate and the TMC 99901 as possible replacements. Has anyone installed any of these? In each case, the mounting bolt pattern in the base is different from the 59128-0000. What kind of material or structure is below the floor in the C27 head? Can I safely drill new mounting holes? I assume that, if I can, the old holes would then have to be patched/repaired. What is the best method/material for doing this? Thanks, Roger