Hi Gino ..... I used the CHR70.3 - Champagne and Silver color combination. Their are both the same drivers.
If ever you would go for the same enclosure, birch ply (19mm) is preferred so that you would not worry on the wall resonance. Of course, panel thickness is also critical. If you are to use ordinary plywood or thinner thickness, you will be using a lot of damping material (apart from the stuffing material) and also internal bracing will have to be added. So using inferior plywood quality may give you savings up front but cost of damping and bracing will be added, negating the perceived savings.
The Pensil enclosure that I have used was supposed to be a very simple build. Using the right wood will really make it simple. In my case, using birch ply, I just added stuffing and its done.
What drivers did JoeyGS use? I too like the cabinets made by Timber. Not a day goes by that I don't look back a page or two to look at them at least once.