Same here. I've ran only my continuous HRT dose of Test on my Tren blasts for some time now, really helps to keep sides under control. Though I tend to run my Test doses pretty low in general.
I've also noticed a huge difference in side effects when running Tren with DHTs like Masteron or Winny. I doubt that I will ever run Tren again without stacking it with Masteron, which is other one of my favorites just like Tren is. Of course this isn't something that will work with everyone, just something that I've learned along the way.
So IMO/IME Def. Keep Test low the whole time, start Tren low and up your dose depending on how you feel/handle it, and if you feel that the total amount of AAS is too low, don't up your Test dose but instead rather add Masteron or Winstrol. One other thing that has helped me tremendously to avoid sides on Tren is remember to keep your blood sugar level stable ie. by drinking small amounts of apple juice, or eating dextrose pills throughout the day (thanks to Stevesmi for this one).
Good luck, and let us know how it goes!