Depends on the size of the boat, and if you want to be able to drive standing up. On my H240, I can stand comfortably under the Bimini, and I am 6'1". So I would say mine is around 76" or more.
Since this is for your H180ss, I don't think you could drive standing up, so you might be right thinking 60-65". What is your windshield height...I think I would go at least 15" higher than the windshield at the center of the boat. Remember that whatever height they sell it as...that is probably the height at the centerline.
Another thought: You can make a tall bimini shorter easier than the other way around.
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"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings