Spring swaps and o-rings are probably the best mods you can do to a steno keyboard.
The purpose of spring swapping to lighter springs is to make it easier to press multiple keys at the same time. You can spring swap without desoldering on the Uni.
The recommended minimum spring weight for MX switches is 20 grams. You can buy 20g springs on our storeopen in new window.
Here is a video showing you how to swap springs on the Uni without desoldering: