I know your original inquiry was to see if someone out here has direct personal experience hauling a B2650HSDC on a single axle trailer, details to be confirmed. You will of course get a lot more in free advice... I may have a data point for you and then a few free of charge comments like the rest.
1) I use a Stage Coach brand 14' trailer to haul either of two B2150 tractors I have. One has liquid filled tires. One has a FEL. One has twin 6" spacers between the rear wheels. Bought the trailer new with heavier axle and wheels, etc. using a 5200 lb axle, 6 lug tires, etc. Your tractor is about 400lb heavier than mine but there is no realistic question that this trailer would be more than adequate for hauling a B2650. Comfortably. Features I really like about the StageCoach model I bought are: Small beavertail which results in a short ramp which results in super easy loading. Also for old men like me it means the ramp is MUCH lighter and easier to handle. Strong pipe type side rails. Nice tie down spots built in. Protected lights and protected wiring. Mesh sides that allow me to haul the wife's mulch without adding ugly plywood sides, etc.
2) All that said there are a lot of considerations and issues (including the ideas mentioned by others.) I'll list what I think matters for you.
-- Is this the only trailer you have in case you want to haul the tractor AND implements like a bush hog etc ?
-- What do you pull with ? Plenty of beef or is a small trailer better ?
-- You said
"I do not plan to trailer the tractor often, maybe once every couple of years, the primary use of the trailer is other utility purposes." I think that says a lot about your application -- just being able to move the B2650 once in a while and MAINLY use the trailer for general purpose utility applications. That leans strongly toward the smaller trailer with a beefed up axle to be on the safe side. You have no real need for anything longer than 14 ft. You have no known need for anything with more load capacity.
-- Is this in the context of a country home with 3 acres, a small 50 acre farm with several implements around or a side issue in a big operation of some sort ?
-- You have to figure for yourself what is the best match for you of course but ...
- smaller trailers are easier to maneuver, esp. by hand. Also to store.
- Being a trailer with sides, make sure you have plenty of width for all cases (belly mowers for example tend to surprise people on width needed)
- You have no need for trailer brakes on that size machine or trailer. Unless you have much heavier things to haul that would be both extra expense and needless bother.
3) You pose a very interesting question about length and space to load the tractor to get the desired tongue weight -- I have found a surprising (and never explained by the manufacturers) difference among trailers in terms of where the axle or axles are placed relative to the long dimension of the trailer. Some have the axle/axles very far to the back and others more to the middle of the load bed. In my opinion you will have no trouble getting optimum tongue weight using a 14ft trailer. Your entire tractor is only 8' 5" long so it will be no problem to get the c.g. of the tractor well forward of the axle no matter whether the axle is mid-bed length or further back. Notice in the picture below of my trailer, it happens to have the axle more towards the rear rather than mid deck. That makes adjusting tongue weight quick/easy.
All those things thrown out there, it depends so much on your individual situation. I have yet to build a building that I didn't end up wishing it was bigger.
I suppose by now we have worse than overkilled your question. Good luck .
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