Marty - I'm not sure why they'd open too easily if less closed to start with...I'm thinking a wedge shaped metal reinforcement between the block and the (Otherwise "V" shaped) plate....to preserve the contact angle at rest...

I could also incorporate an elastic band between the two eyes to make it require a predetermined amount of opening weight to open/extend, etc...if I need to.

On the shock length's....are you saying you needed to get about 29.5" extended length shocks...or that that's where you measured your droop from arch to hub center?