Just about every ductless AC we install falls short of the minimum . Most homes have a very limited area to set the outdoor unit and we always try to keep it as close to the indoor units for aesthetics . Been told coiling the line sets behind the unit is a no no . Been told to zig-zag the lines sets along the outside wall , but who's gonna want to see a racetrack on the side of their house ? Also been told to coil the line set horizontally on the ground . But that just seems like an accident waiting to happen .
Anyone install these with line sets less than the minimum ? Any issues ? Anyone upsize the line sets ? ( told that was a no no too ) .
I'm surprised that you are almost always at the minimum
I will reference Fujitsu as that is what I know best. Laying the line set off in a serpentine manner behind the unit is best. Coils are absolutely a no no. Traps oil. Increasing the line set may be convenient for you but if you call engineering asking for a charge on an up sized line set they won't even talk to you. They will simply say install it per the specs. The mins are 9' for 9, 12 & 15 kbtu units. 18 and up is 16'. Confirm those numbers?
The first year the inverter units came out, we were told that you could get a resonance out of the evaporator if the line sets were to short. Some time later I was with one of the Japanese engineers and asked him what the noise was. He said it was the compressor telling you it is unhappy.
I'd suggest sticking to the specs for warranty support.