Nope, the problem was fixed pretty well already by the NoFlex down the shower
drain, apparently clearing out some clogging in a sharp hose bend underneath the shower
drain (see previous post, as well as Roy's posts).
I just didn't like leaving the job half done - eventually all that crud in the sump box would have caused a problem. The strainer cylinder was getting pretty caked with gelatinous muck. Will see what the maintenance
interval is - this was my first after living aboard
for 9 months (and I doubt the previous owner had cleaned it either). The hose bend really only started clogging within the last few months.