I think you will find that typically the 35 mm motor will have a higher listed current rating for continuos use.

The 35 will run cooler.

Depends on length, it can be that short larger motor will withstand less current then long 28mm. Weight gives usually better orientation. Heavier will give more power.

IF the length is the same, then that larger will have lower internal resistance, better radiation and therefore will withstand higher current, probably will have also higher no load current.

I originally thought this 28mm I have would be a good motor, but then I thought that it was likely with the size of the plane and the weight that I would probably burn it up. Thus the thought of putting a 35mm motor in. There's room. The plane is about 610 squares and will likely be about 60oz ready to fly or so. Both motors are about 770kv (well one is 760 and the other 780).

My 109 stunter flew on an Eflight 25 and 4 S, it was 650 squares and 63ounces as I recall.

It was 870 KV though, and I seem to recall Mike H saying the 25 did not like a 5S setup,, so it might not be a good way to go, but the 35  mm at that KV should be ok I would think. Whats the rated power continuos ( watts or amps)

Well, I picked up a 35mm motor to put in - and it doesn't fit. Too long. So, I will modify the mount to accept an EFlite 32 as it is a bit shorter and will fit in the hole. Fun things, these toy planes.

What was the question about Randy?  Length or Diameter?  I still stand behind my statement that a cobra 35 series will run cooler than the 28 series.  Trust me I know.

I was initially looking at a Cobra 2826/12 or a Cobra 3520/12. I set it up for the 3520/12 figuring either would fit then. Thus the question. I also picked up a 3525/10 mostly because it was a bit lower kv (820 versus 780) but he 3525 is about 3/8" longer and weighs another 80g compared to the 3520/12. It doesn't fit and is too heavy. Fine. Could go with the 3520/12 or just modify the mount slightly (elongating the holes a bit) and use an E-Flite 32 (I have a box of those). It's the same length as the 3520 and about the same weight. And I know them a lot better.

The question here was more is there any benefit to going with a larger diameter motor - what are the benefits and drawbacks. I had a 2826 that I've never used and thought it might be a better choice to keep the weight down - but only if it would work. You guys convinced me that a largely diameter motor would be a better choice so I started looking at what I could use. Decided that going with a set up I have experience with is a better choice.

I'm still learning this stuff and can use all the help I can get.

Randy, i have used Cobra 2826/12 to pull my testbed - TF Score (680 sq in, 65 oz), close to max length lines at 5.3 sec lap, and measured temp upon landing using laser thermometer-  its within acceptable range.  610 in/60 oz should be a piece of cake for that motor.  5s battery, start with APC 12x6 prop.