The International STa"M Forum

The psak I received from Rav Gavriel Zinner (Nitei Gavriel) some years back is that filling in the letters is permissable and not an issue of maase uman. He also suggested ensuring the eitz chayim were sewn on before Yom Tov, otherwise it should be done by a goy on chol hamoed and re-sewn by a yid after the Chag.

All you need is hot water and a syringe. Pretty simple solution for a very annoying problem.....