Honestly, if you're already injecting the tren ED, I would do the same with the prop, at lower doses. Same syringe. 20-25mg daily comes out to 140-175 a week, and for the sake of consistent blood levels, I don't see why you wouldn't do it. That's how I personally run my cycles. Of course, I don't know what size syringe you're using...not sure if you can measure out 20-25mg with the tick marks available.
If you don't like that idea, I would still try keeping it to E2D, and then each week you'll have differenct days that you're injecting prop. That nearly-3-day-break over the weekends would probably mess with me quite a bit.