Gorgeous work! I’ve done counted crossstitch and needlepoint and, as someone said, make sure you square before quilting. I wouldn’t think you’d need to stabilize as 27 count has small holes. Check your batting for how far apart you need to quilt. Personally, I love Quilters Dream wool batting (I think it’s every 8” for that). Since they are big pieces, I might consider Quilt As You Go (QAYG). Check YouTube. Also with QAYG, it might be easier dealing with the thicker fabric. On second thought, I’d consider paying someone with experience to quilt it or I’d hold on to them for a while until you have more experience. Good luck. They are beautiful!