opinions please on indoor ring size

[babalina]

My husband and I bought a small farm 1 mile down the road from our dairy farm. We were restricted by distance to the cow farm. I have a horse, here on the property and is being boarded over the winter. The indoor there is small and the sand is way too deep and my horse is laboring trying to get around. here is a video of the deep sand ring
http://www.youtube.com/watch?v=MgUV9z0nG1o

On the house property, is a clear span building. I measured the outside 36' by 64'. 1/3 of the building has a concrete floor and used to hold heifers. this indoor would only be used by me. do you think that this would be way too small? I need to know before we take up the concrete, etcetera. I already know it is small but would it be 'ridiculous'.

fast fwd to 3:14
http://www.youtube.com/watch?v=qjZA1X2g4r0

[Bluey]

Our neighbor added sand to the concrete floor of an old Quonset barn, 50' by 60' and "lopes" and trains his cutting horses there in bad weather and on a mechanical rope cow strung along one long side.

I think that in any less width it would be hard to ride more than at a trot.

[Mallard]

IMHO, 36' is much too narrow for anything but walking.
That is only about half the width of a dressage ring.

[4Martini]

The barn I'm at has an indoor that is 50' X I think 80' I would say that is the bare minimum for riding - and not that pleasant but great as an option. Now, it would still be nice to have an indoor area for ground work, rolling in the winter and vet appointments etc. Probably not reasonable to canter in though- maybe a little trot work.