What are the safest dose constraints for moderately hypofractionated prostate cancer?

At Penn, we have a protocol for 70 Gy/28 fractions using proton or photon therapy for low- and intermediate-risk patients. I initially designed it with a conedown as follows, but that is not always necessary/appropriate.

CTV Initial = Prostate and proximal seminal vesicles to include at least 1 cm, ...

This article by @Dr. First Last gives good overview and dosimetric constraints for moderate hypofractionation (70 Gy in 28 fractions).

The PROFIT trial is now published. The strengths of PROFIT are the strong comparison arm of 78 Gy in 39 fractions and the straightforward treatment planning parameters (CHHiP is very hard to figure out...at least by a simple man).

In favorable IR patients, they only treated the prostate and the CTV-P...

I use the Fox Chase Hypofractionation protocol as my hypofractionation guide (currently I am offering it on trial randomizing 70.2 in 26 fractions v. 36.25-40 gy in 5). PTV margins were tighter in this trial than Profit.

For the Hypo arm (from FCCC hypo randomized trial):

Bladder: Less than or equal...