I dont think he should have any problem suspending that amount of prop at 5%. Like you have seen in other threads I comment on I run my prop at 100mg/ml and brew it at 3% BA and 3% BB and it holds fine, plus ity is a smooth pin. Since I had not brewed Sust I was not sure if the mixed esters would change that. I would guess not, but I guess you never know.
Hopefully Energy will post his results.