I built the 75mm 7x20 version with BetaFPV 17.5K motors and F3 FC w/OSD and it was lethargic and pretty disappointing with the recommend 230mAh batteries compared to my Beta65 and Beta65s. The 260s weren’t any better and both batteries got extremely hot and only gave about 2m flight time and I’m sure it was killing the battery longevity.
The 75mm frame was built for much larger batteries like my eflight 550s but they were just a tad too big for the holder. Then I noticed BetaFPV put their 1S HV 550s on Amazon so I ordered a pair and they made a tremendous difference. It’s like night and day for punch. Plus I get over 4 minutes indoors and about 3 minutes ripping around the back yard going full out as much as possible. It’s an entirely different quad. The IR of the 550s are about 83mOhms compared to the 230’s 120mOhms so the 550s are delivering the current the 7x20s need. I likey!
Anyway, Amazon up their price on the 550s by $2 a pair to $17 (in one week). While looking for the better price on the BetaFPV site of $13 a pair, I noticed they have the 75mm 8x20 and 85mm 8.5x20 versions of the whoop frame (which by the way the 75mm 7x20 frame is extremely durable).
Since they stock the motors and props for the 8x20 frame, I was thinking of picking up a frame, motors and props to test out when I order some more 550 batteries but I wanted to ask the folks here. What would be the benefit of moving to the 85mm 8.5x20 frame and motors? The 85 also goes from 40mm props (75mm) to 48mm props.
Would the 8.5x20 be more efficient for longer flight times like my Blade QX2 (6+ minutes) or would it just provide more power and less flight time?
I guess I could order both and try them but dang, a guy can only have so many whoops, right ?!?