What dose constraints do you use when palliating pelvic structures in 5-10 fractions?

Very much depends on the total dose being delivered.

If doing 20 in 5 or 30 in 10, I don't believe any structures in the pelvis are at risk for substantial toxicity, for acute or late.

If going higher, then utilizing SBRT/VMAT constraints for the pelvis is reasonable. Can use @Dr. First Last' method...