Interesting. I don’t remember having spring trouble with the Holy Bobas.
I tried 63.5 regular Spirit, and 68 G Progressive Spirit.
I really enjoyed the 68 G Progressive Spirit springs with Holy Bobas. Being light at top, the spring made the stem pretty tactile, but 68 G at the bottom helped it reset.
If going lower than 63.5 G, I would use Long springs as suggested, as they seem to help with marginal weights in the Boba housings generally. For example, 57 G Long is a safer weight with U4 Boba than just 57 G.