Good morning mama! From what a few of us mums experienced, maraming cases talaga na umakyat ang placenta from grade 1 to higher grades by third trimester, kaya there's definitely hope pa for you, honestly the fact na umakyat na sya from 27 to 35 weeks is a good sign! I'd still check in with your OB about your activity level though, kasi bawat pregnancy is different at gusto natin sigurado na safe ang routine mo given your situation.