Yes, the cubes would be the same as hay - or you could use soaked hay. Don't worry about the temperature effect. It is what it is!
--
Eleanor in PA

www.drkellon.com 
EC Owner 2001
The first step to wisdom is "I don't know."

If you are using the pads inside the Soft Ride boots that is enough cushion. Letting him out is fine. Some of the soreness is often from poor blood perfusion and movement helps that. If that is the case, you'll see an obvious difference in how he is walking between when you first put him out and after he's been out a while.
--
Eleanor in PA

www.drkellon.com 
EC Owner 2001
The first step to wisdom is "I don't know."