Boost Actuated Exhaust Cutout

As a bigger turbo is in the works I've been considering changing from my 2.75 inch exhaust to a full 3 inch setup. But I really like the look and sound of my current setup so I started looking for other options.
 
I came across this setup done by Texas_Ace that has an electric cutout added to the dp that can be opened and closed from inside the cabin. When open there are no restrictions so you can get the best possible flow, and its also super loud :D
 

 
The major downside I see with this is that you need to tune the car in the open position so it won't run as well when driving around with it closed which if you drive the car around town alot will be most of the time, not to mention it takes 5-8 secs to open and close which is a little slow.
 
Enter the boost actuated cutout which uses the actuator in place of the electric switch to open and close the valve. Its much faster and can controlled a few ways eg. by a boost controller just like you would a normal wastegate. It has a much quicker response time and once setup it will open automatically when you hit boost and can use the extra flow!
 

 
Has anyone done something like this in Aus? I'd be keen to hear anyones experiences even with non MR2 setups

I have the Greddy Power Extreme which I'd probably like to avoid modifying since as far as I'm aware there aren't too many around.
 
Atm I have a 3 inch Berk Dp going into the 2.75 inch PEX. I have another 3 inch dp lying around that I'm not using which I would use to experiment with if I do decide to try this!

Alot of people that have gone with these cutouts have used them have used ecu's like that. Some pretty interesting setups to using throttle position or cruise control buttons to open them!
 
The police certainly wouldn't like it but I think unless you blasted past them with it open they should never find it :) Definitely a risk though.
 
So you don't think 2.75 inch piping is going to be much more restrictive then 3 inch? 300kw is the goal of the build and I was under the impression the a full 3 inch system was best for that kind of power??
 
EDIT: Just realised you meant changing the b pipe to 3inch and retaining the muffler sections would flow enough for 300kw?
 
If thats the case that is what I'll probably go with, I want to keep the PEX but only if its not going to be restrictive!

Steve_A
I have the Greddy Power Extreme which I'd probably like to avoid modifying since as far as I'm aware there aren't too many around.
 
Atm I have a 3 inch Berk Dp going into the 2.75 inch PEX. I have another 3 inch dp lying around that I'm not using which I would use to experiment with if I do decide to try this!

The main glory in that PEX would be the mufflers. I'd definetely recommend changing the mid piping (not the Y-pipe or mufflers) to make it 3inch from the turbo to the Y pipe. I don't regret for a second ditching the 2.5" mid pipe on my HKs SuperDragger.

I would bet that a regular 2.75 inch pipe would flow better than a 3 inch with a big ugly butterfly valve stuck in the middle of it anyway.
When stuff is getting as hot as dump pipes do I reckon less is more. Less welds, less bends, less joins and less mechanical bit and pieces.
P