I got the LaBella steel flats and installed:
As expected, the flats tuned up to pitch right away and stayed in tune. They are narrower in gauge and definitely higher in tension than the rubber strings. Since the rubber strings are very thick and have more vibrational motion due to the much lower tension the nut slots are thus cut very wide and high:
I bottomed out the bridge in an attempt to lower the action:
Despite those adjustments the action remained very high for the flats:
(You can see where I painted over the original side dots that were between the lines and painted on dots that are on the line, which I prefer).
It was overall still playable although at the first fret it was definitely harder to press down. If I were to keep the steel flats on I would have a new nut made and the bridge somehow altered to get the action lower. I'm not into such heavy modifications just yet, so I put the rubber strings back on. I will contact Gold Tone on Monday to see if I can get a new G string under warranty as the one that came with it is getting more tweaked.
After trying out the steels, I strangely found myself preferring the rubber strings. True, they are a pain to tune up: you have to keep lifting the string at the bridge and nut after several turns of the tuning key to keep it from catching on either end and possibly stretching it to the damage point which is apparently what happened to the G string at the factory. And baby powder definitely helps with the playability. Soundwise both strings are viable, but the rubber strings are more....what's the word? Funner?? I suppose if the flats had nice low action without any costly and drastic mods I would probably have a different assessment.