I’m just about to buy some TX springs for my Holy Bobas – I only have the 62g variant from the U4Ts + the original Drop Halos + some spare springs from my Gateron Black Inks – none of them seem to work well. I agree with your statement that all the springs seem a “stiffer” on the Holy Bobas (not merely that there’s an issue with the return).
Would you suggest me to try the 60g or 57g (which is what I can find nearby) or perhaps I should get both packs to try…?
I prefer to use 16mm long springs on this modified switch. I have settled on the 60g
but it is my preference. The halo stems may be even easier to work with… but I can’t speak on that unfortunately because I have never tried them . Ultimately as you have mentioned “trying” different scenarios would to be to your benefit. I order from mekibo for my TX brand springs…
Best regards on your builds… cheers! 
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.