Extremely successful relative to what? Not using AAS?
You'll gain no matter how you shoot it, but we're in the business of optimizing things to gain as efficiently as possible. Knowing the esters in sust, it logically follows that ED injects would be ideal, EOD at the least frequent. If you want to inject less frequently, just switch to a single-estered test that makes more sense, based on the intended use. Also, 8 weeks of sust is poor utilization of something that is made up of 1/2 longer esters. You won't even really reach a point where you'll be at peak plasma levels to fully take advantage of sust.
No problem starting the tren at a low dosage and moving up, although 20mg/day is very low IMO.
Since you have the prop anyway, I'd say go ED injects with prop and tren for 8 weeks and actually fully utilize all 8 weeks. otherwise, switch to a longer cycle and incorporate the sust