Are Hair Extensions for fine, weak hair if done correctly?

Hair Extension Experts-This is for you. I myself am a stlylist and owner of a salon on the east coast. I am 36 yrs. old female, and was diagnosed with hypo thyroid 6 yrs. ago and had to have it removed. Now I am taking synthroid. My hair was thin and weak before the synthroid and over the years it continues getting more thin and easily breaks. I spend quite a great deal of time styling it, using lots of thickening products and have used Rogaine 5% for the past 5 years. Now, my dr. is suggesting some type of mineral steroids because my blood pressure is very low. It has gotten lower over the past few years, and I often get dizzy, and have a very hard time getting up in the morning. Five years ago, I got a BAD extension job done that nearly cost me the hair I had. It was a weft, attached to horizonal braids made up of my own hair. WAY TOO TIGHT and had to have them removed the next day. I would have lost all my hair for sure, if I had kept them in any longer. Anyway, I cannot believe it, but I am actually considering having them done again using a different method. I have been talking via the internet and telephone to different ones using the great lengths method. It is supposed to be gentle and leave your hair in as good or better condition. My biggest concern is the weight of the extensions and the attachment method not harming my hair. Of course, my goal is to get come length to my hair and not have to cut off any hair once they are removed. Will this work if the strands being attached are thin and the very fine hair is used to prevent weight on the hair and follicles? I am trying to achieve volume more than anything, so I don`t have to spend as much time using heated styling tools and so much styling products that may not be healthy for the hair. Please give me any info you`ve got. I really can`t afford another mistake like the last. Thank you so much for your help. If I can get the results I am after, I would surely check into incorporating this into my own salon. I`d love to give others that kind of satisfaction and relief.