I aso have the Mahalo uke-guitar (UNG-30). I recently got the Yamaha GL-1 too. The Yamaha sounds and looks better, but the Mahalo is a very good deal for the price. (Now available in red, blue, or black from Amazon.com for $35 postpaid!) (USA). The Mahalo fingerboard is less cramped though, being about a 19" scale.
I actually had the Mahalo for a couple of years, but most of the time thought it was junk, a gimmick. I still had the original strings on it, and was tuning it to standard guitar tuning. Recently I put new strings on it, and tuned it up a fourth to guitalele tuning, and now it sounds very nice. (The stock strings they put on it are absolutely terrible, can not be tuned to guitalele tuning, sound miserable, etc. I just put a set of cheap (D'Aquisto-$3 plus at Elderly.com) normal tension classical strings on it, and that worked fine. I don't feel any need for higher tension strings.
On the contrary though, I found the stock strings that came on the Yamaha GL-1 to work and sound fine (and hold tuning) , at guitalele tuning. So, haven't changed them. When I do though, I wonder if it would be better off with high tension strings, having a shorter 17" scale? (I did unfortunately find the action too high. I had to pay a local guitar shop $40 to fix the action. Now it plays fine, although of course cramped with that scale, on a 6-stringed instrument.)
Or, I wonder, if the GL-1, having a tenor uke body and scale, might sound better (instead of a classical set) to use a tenor low G set (Worth clears, perhaps?) and then use two individual classical guitar 5th and 6th strings for the last two? (The problem I would have with that--which strings (available individually, or in a bass set) to use on the 5th and 6th strings, to best match the uke strings on 1-4? Anyone here tried the Uke on 1-4, cg on 5-6 combination, on the GL-1? If so, which combo did you find to work the best? (One difference if one used the Worth low G set on 1-4, compared to just using a guitar set for all 6, would be that the 4th string would be unwound. Not sure how that would affect the sound.)
(OT) By the way, there is another guitalele readily available in the USA, online at least--the Aria ATU120/6. (I think that is the correct model number, not sure. (They don't call it a guitalele, but that is what it is.) More expensive than the GL-1--all stores that have it charge the same price--$160. Has anyone here tried one of these? What is the scale length? How does it sound compared to the Yamaha GL-1?
I bought a Mahalo Ukulele-Guitar, which is pretty similar to the Yamaha (slightly longer scale). I tried various combinations of strings, including Aquilas (both baritone & tenor) like you did, but eventually settled on a combination of D'Addario Pro-Arte classical's in various tensions, stringing it ADGCEA (up a fifth, so like a uke). It now projects really well, has better resonance, and feels like the strings are at the right tension.
So, I'm using...
A - Di'Addario Pro-Arte Classical Guitar, EJ44, Extra Hard Tension
D - Di'Addario Pro-Arte Classical Guitar, EJ44, Extra Hard Tension
G - Di'Addario Pro-Arte Classical Guitar, EJ44, Extra Hard Tension
C - D'Addario Pro-Arte Classical Guitar, EJ46, Hard Tension
E - D'Addario Pro-Arte Classical Guitar, EJ46, Hard Tension
A - D'Addario Pro-Arte Classical Guitar, EJ46, Hard Tension
This seems to offer the best sound, tension and feel, and would also work on the Yamaha Guitarlele in my opinion.