I used Martin M620 (yes the TENOR set) on my concert Flea. They are a little heavier gauge than the M600 set, and with slightly more tension, they drive the top more, and produce more volume and have a great tone.
I've been using these Martin M620 strings on my concert Flea now for about 4 years with no signs of any harm to the instrument, however, proceed at your own risk
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Before anyone asks, no these are not the same physical set of strings for 4 years, but I'm changing them when they wear out, which is evident when intonation problems appear, but they last a long time for me, and I've tried other strings, and always come back to these Martin M620 strings.
Strings are as subjective as anything else. A set of uke strings is $5-12, so why not get a few different sets and experiment?, especially since changing strings on a Magic Fluke instrument is easy as can be.
You might find lots of other helpful info in strings in the Magic Fluke Company Appreciation thread here:
https://forum.ukuleleunderground.co...7-The-Magic-Fluke-Company-Appreciation-thread