OK lets see second cycle and have never tried tren or mast before obviously. Not as an absolute rule, but often times higher doses of test when paired with higher doses of tren lead to the imfamous tren sides. I will hope and assume you know what they are. However, and speaking of BBB this was a protocol I learned from him years ago and have successfully followed myself on my last 3 tren runs.
By keeping test down to virtual TRT levels say around 200mg a week total, imfamous tren sides do not appear. To give you some context since I havent been around much in recent months and many of the names here are newer, I have ran 1G/wk of test and 400mg/wk of tren before. It was nice for strength and mass. But I could not breathe, I had 160/100 BP, pulse sky high, constant need to hydrate, night sweats, and borderline sexual issues [arguably only combatted by enough caber].
Then BBB turned me onto the above referenced protcol. Running 200mg/wk test I have run as much as 700mg/wk of tren and BP was still 115/75, aerobic capacity was not compromised. Basically I would say I had 1/10th the tren sides despite nearly double the tren dose. Alongside this 200 test 700 tren I have also run mast anywhere from 400-600mg/wk. I no longer cycle per se in that I blast and cruise and am always on something.
I do by definition cycle the tren in 6-10 week waves maybe once or twice a year depending on various factors. Its also very true that will almost all compounds there is a point of diminishing return. Speaking from experience 350-400mg a week of tren is 80-85% as effective as 700mg a week. So to address the OP 50mg TRA/ED is a very fine and common starting point. I would however, drop that test prop dose almost in half. Granted 350mg isnt really that much.
My own experience finds my max toleration for test to be 250mg a week when paired with tren. Well whats an extra 100mg a week you might wonder, well try it and see I guess. If you get any of the classic tren sides reduce test and I bet they dissipate. Mast dosing dose not seem to worse the tren sides.
However, too much mast for some can create literal discomfort from being too tight so to speak. Training on mast and tren without adequate hydration is begging for cramps et al.
I cannot give you the science behind why low test high tren works I just know it does. Perhaps if BBB cruises in here he will lay the science down.