It is my understanding the
spring/over-center link should maintain a down & locked gear without any
help from hydraulic pressure. <Earl>

Earl-
You are correct that spring force alone must lock and hold the main gear
overcenter link.
Several years ago, I installed the "rat trap" springs (which were developed
purely for appearance) and right away saw that they exerted a lot less force
in the down-locked position than the original "screen door" springs. In
fact, their design is backwards...they exert minimal force in the down-lock
position and maximum force at full retract, the opposite of what is
required.
I threw the rat traps away and went back to the original "screen door"
springs (two per gear). They exert their maximum force in the down-lock
position and are more than sufficient to snap and hold the overcenter links.

Bill Rumburg
N403WR (Sonic bOOm)