Crowe, I really think you'll get better results buying individual herbs and taking them together than you will from taking an herbal cocktail such as Estroven. Not that Estroven doesn't have good things in it, but you probably won't get enough from its ingredients to produce the results you want. Then again, if it's working for you, who am I to tell you to switch. Herbs are strange, and if you find a combination that works for you, it might not work for someone else. Unlike chemical hormones, herb use is based on tradition and word of mouth, not clinical studies. However, my personal experience with herbs and some of the information I've gotten from others who've used them is that full doses of various herbs taken together usually get the maximum results offered by herbal therapy.
Red Clover is a good phytoestrogen, so if you're taking Estroven already, that should be a good combination. I've gotten good results (well, good for herbs) with Red Clover and several other herbs together.
Everyone knows that chemical prescription hormones shouldn't be taken without consulting a doctor, but I know many trannies experiment with them anyway. Not that I condone the use of chemical hormones in the absence of a doctor, but if you are going to use them, you really shouldn't mix herbal hormone supplements with chemical hormones of the same kind, based both on my research and what I've been told. For example, don't take Estradiol and Black Cohosh together, because they both affect estrogen levels in the body. Also, don't take Saw Palmetto (a phytoantiandrogen) with a chemical antiandrogen, such as Spironolactone or Cyproterone Acetate.
As for using herbs and chemical hormones of different types, I haven't found anything that suggests that's unsafe, or that there are any negative interactions among any of the specific herbs and prescription drugs I'm using. For example, I've been using chemical antiandrogens to block my testosterone while using phytoestrogens and phytoprogesterones to increase my estrogen level.
I wouldn't recommend using birth control pills alone to feminize. If you're going to move from herbs to chemical hormones, you should use the ones developed for HRT. I'm not an expert, but I've never heard of a doctor prescribing contraceptives for M-to-F feminization, unless they are part of a multi-drug prescription. I know some drugs used to prevent pregnancy are similar to drugs used in HRT for females and HT for M-to-F trannies (I think Provera, for example, is used for both), but to use a drug for HT that was specifically designed for birth control is probably unwise, unless a doctor specifically prescribes that drug for you. Even then, in the case of Provera (Medroxyprogesterone Acetate - a progestin), the doctor would probably prescribe some form of estrogen, and possibly an antiandrogen, to go with it. Maybe some of the other girls can verify this for me. I know just enough to know how dangerous it can be to misuse these drugs.