mooring pendant - E32-2

I will be mooring her in the Spring in a bay here in Long Island, the WM catalog and others sell 15' pendants and say to use a pair.

Previously, I made the mooring pendants, and would like to do that again, I figured a 3/4" dia line and wonder if 15' is too long/short?

FWIW my boat is moored on Long Island Sound to a 2500 lb concrete block to which is attached a chain shackled to a 1" nylon line supported by a mooring ball. I have twin 3/4" pennants attached to a loop spliced in the 1" line. The pennants are about 15'. The tide change (7 feet) is accomodated by the 1" line, not the pennants. Assuming that whoever is installing your mooring tackle is qualified, he/she should know what's best for the local conditions.