What sort of angles are you planning on running?
I will say that I personally see no problem with a 27.2 waist, and actually think I may go for something in that range for my next split. One of my reasons probably doesn't apply to you guys, which is that I weigh 210 and thus have no trouble going edge to edge on a wide board and it helps me float in backcountry conditions.
HOWEVER, the other reason is angles. I will say that on a split, rocking forward angles (which I still do) does have its limits, and I have to ride shallower angles, which can mean a wider board helps if in crusty conditions (powder = who care's about boot out). Because of the inserts for uphill touring, I become limited in terms of being able to keep a fairly narrow stance (which I am used to... 20.75 - 21 inches). With that setup for me, I have to drop my angles to about 27-12 or so. I'd really prefer in the range of 36-21. If I ever did a custom split I'd ask if they could offset the uphill inserts to allow for more space for forward angles...
In the photo you can see that I have to ride with my right riser up and my left toe piece up. Anybody else played with these more than me to find the right angles?