Sounds good my first cycle was test E for 12 weeks at 500mg/week.
Personally I would go with 500 a week, but if you want to start with 300 go for it. To me that is just slightly above normal levels and you will most definitely shut down your natural test levels post cycle.
How many grams of protein are you getting per day?
@cdoubleu
For your question on an injury, I had a pretty bad broken leg (open fracture). Once I was able to move around a bit I took 200mg of test and 200mg of deca per week. Hit the physio hard and made a full recovery.
Also: I don’t think you are nowhere near 20%bf. I would estimate you 12-15% from the picture I saw.
Looking forward to your progress. Let me know if you need any help!