re: Learn me about Mini Split AC Units w/ extended line sets

I recently installed a MR cool cassette style at my parents and it came with a factory 25' line set. Like you we installed it further away and went with a 75' line set, after vacuuming it down we checked the pressures and it was fine. So we Didn't have to add any, not sure that helps lol.

You should be able to fine a line set that will match the fitting size or like you said make your own with a cutter and flaring tool.