You definitely don't need to go down to an 11" riser to pull that off. Narrow deep core limbs rule on long bow limbs... look at the Shrew design Mike... Those are built in 52" length....but they are one piece.
i built a few of those in a TD formate years ago i called "The Yeti" that had both RC limbs and hybrid long bow limbs.... but the shorty bows never really sold well, so i took them off the line up and quit building them.
Here is a 52" prototype that developed a bit of noise in the fade area that i hunted with for a couple years, and hung it on the wall of my shop. I revised and lengthened the riser fades after this one, and had much better luck.
Same bow at a 3D shoot being drawn 30"
Here are the 52" TD's with RC limbs. both of these have 16" riser