I got Forge (without a "d") actuators on my newest build.
I got them specificaly cause of the dual port option.
This because i anted to be able to run as low boost as possible, when needed, but still be able to run as high boost as i wanted too.
I set them up with a 7psi spring... However...The springed chamber is not sealed against the rod when you get them. But you can get theese rubber seals for them. Pictured below. 
So i did! However looking at them prior to the install i thought that "hmmm... will theese be able to hold up?"
So i installed the boots and tested with a mightyvac.
They still leaked past the rod although not as fast as without the seals. So i tried a hoseclamp on the end of the boot and voila. Sealed! Now the springed chamber would hold boost. Installed the things on the engine and got the car back together.
I had a 7 psi spring in there and it worked flawlesly.
7psi at low boost and i had it up 25 psi at high boost.
I have two 4 port solenoids (Mac) hooked up to my aftermarked ecu to control them. But you CAN try to just swap the solenoid on your prefeered boostcontroller. Although because of the heavier interia of the 4 port solenoids they prefeer to be run at lower hz (about 10 hz) than 3 ports. It i still doable but you will not get the same controllrange at 20hz.
The setup works as follows.
When low boost is wanted boost is directed towards the "regular" chamber to blow the gate open at 7 psi.
When high boost is wanted boost is directed towards the springed chamber so that the gate is held shut with the combined force of the spring and whatever boost you are running at the time.
Anyways. It worked.... for about 10 minutes of boosting. I have datalogging setup to log automaticly at a power run so i can tell how long it ran on boost.
Suddenly the car felt slow and by the datalog it shows it is running only 18 psi.
Had a sneaky suspicion and pulled out my mightyvac again.
And yeah... my passanger side springed chamber was leaking boost. This meens engine pull.
Did that last weekend and them emailed Forge about the incident. After a few emails back and forth it turns out that Forge never intended theese actuators to be run as dual port actuators at all. The boots is in reality DUST boots, not boost seals, ment for the Lancer EVO 5/6 actuators in their range.
The extra port on the clock is ment as a breather hole to mimic some OEM actuators where it is desirable. Letting it breathe helps response.
So there is that... That said i have come up with a new plan to acheive my desire of a wider boost range than normal.
I belive the boots will hold up just fine with vacuum instead of boost. So now i will install a heavier spring (14 or 17 psi) and hook electricaly controlled vacuum up to the springed chamber to get lower boost. Now at the low power setting boost will press on the spring to open the gate at the same time as vacuum will PULL on the spring.
When i want higher boost the vacuum is released and the actuator is controlled normaly. I now need to go back to two 3 port solenoids tho... Im probably getting my replacement boots from Forge in the mail today so hopefully i will get the engine back into the car within the next few days.
If the boots fail down the line now only my low boost setting will be affected and the actuator will still function as a regular single port for high boost. So no NEED to pull the engine if that happens. As for quality of the actuator itself.
Well it is no longer diaphrams in them but pistons. 
Theese are sealed up with two o-rings and is lubed up with grease of some sort. So the problem with ruptured diaphrams in no longer a concern. Time will tell if seized pistons will take over but i do have faith.
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