I haven't tried the AR formulas, but both of my kids had the same thing and we used the Simlac Alimentum because it doesn't have the milk problems in it. My daughter could use some soy, I think we did about half and half, but my son can't tolerate the soy either, so its pure alimentum for him. He is 5.5 months old and he is throwing up rice when I feed him, so we are taking a break back from foods for now. Spit up happens, its the nature of the GERD, but I would not recommend a fussy baby because they are crying because it HURTS and I wouldn't want feel that if I didn't have to. When we put the rice in his bottle he wouldn't drink as much so he woke up hungry at night. When my little guy was that age I would feed him 4 oz every hour and a half. This meant we fed a lot, but he didn't spit up as much and his tummy didn't get overwhelmed with too much food. Also, have you tried the playtex dropins? They help keep the air out, and the latex nipples are much better than the silicone ones if he has problems latching. I hope this helps, but if you need more help pm me and I will see if I can help. Good luck!!!