Pool Pump calculations.....help?

[1PoolNoob]

+ Restricting flow on a centrifugal pump does not cause overheating, so long as sufficient water passes through the pump, to prevent the water itself from getting hot. One GPM is sufficient to accomplish this.

+ Restricting flow to 1/2 of maximum will REDUCE electrical consumption.

+ The only way to measure the flow is with a flow meter, OR by discharging the flow into a container of known volume, and timing how long it takes to fill. BUT, you can 'feel' the flow, and tell when you've reduced flow rates by 1/2 or more.

+ Flow rate of the SuperPump depends on your piping AND on which "3/4 HP" pump you have: uprate or full rate.

Interesting, I've never heard of restricting the output of the pump to get a desired GPM. This is the pump I'm looking at getting (ITEM # SP2605X7A) :
http://www.hayward-pool.ca/prd/In-Gr...93_.htmhttp://

How do I tell if it is a centrifugal pump and whether it is uprate or full rate?

So basically you can block/restrict half the output of the pump and it will cause the pump to work less, lower amperage consumed..? Does doing it that way, in essence, have a similar effect to that of a 2-speed pump?