I used the two outlet tips as in and out, I have cut it with a cutting disk, the inside will slide out, there is a packing glass between the perforated 3 chamber chicane and the stainless shell, the insides are very heavy.
I have cut the first chamber and screwed it at the very back using the screen to damp the pulses and have drilled holes around for flow. The cops here measure the depth of the inside tube so it saves me tickets as well.
Unfortunately it's still too loud for me so I will get a perforated tube, weld it on the center axis and pack the outside, this will lower the frequency.
Note that the turbo is quieting the tone a bit too, but to my surprise, not by much.
On the pics you see the muffler with the first section installed and the two remaining chamber cut between section one and two.
The exhaust trough the center cone that you see at the exit of my exhaust and then travel to the chamber 2 trough an offset tube, then tumble in the second chamber to go trough another offset tube... heck of a maze.

 

If you have the skills and the tools then I'd say go for it. But if the end result is more sound I'd say to at least first do more than just drill a few holes in the stock pipes. If you drill all around and remove the first baffle, then get a long drill bit and drill some holes into the next baffle, you'll get basically the same sound as a set of aftermarket pipes for free and for a lot less effort.

 

Being new to the VTR and all, what is in those cans that makes them SO heavy? Simply drilling holes will only change the sound and wont provide the benefit of aftermarket slip ons, right?