Hi Steve,
Relays take the current away from the switch making the switch last longer. My suggestion would be to get an adjustable thermostatic switch where you can put the probe in a water jacket (on the water pump is a great spot), then from the adjustable switch to the relay and from the relay to the fan.

Pusher fans need to have a lot more CFM's to do the same cooling capacity as a puller fan. So if you are going to put a fan in there, it might as well be the biggest one you can get. Otherwise, why do it if it is only going to marginally help. Fan Shrouds work the best on Puller fans where it forces the air to be sucked through the radiator and not from the sides of the fan.

No help on the Summit fans. My friends and I tend to do somethings only once and fans are something we only do once. So it's SPAL for us.