Got some bad news today…apparently a neck/back injury I sustained from a car accident last summer hasn’t fully healed. I got my 36er about three weeks ago, & have been riding it nonstop. I’ve probably done at least 150 miles since I got it, ending with a beautiful 22 mile ride the morning of the 4th (last Saturday). Since then, I’ve had pretty severe neck/shoulder pain & headaches. I went to my doctor today & we decided that I should start physical therapy again, &, if that doesn’t work, move on to other options. So it looks like I’m grounded for a little while. No Seattle munifest this year 
You might just need to adjust your set up. Do you have handle bars on your 36er? A proper handle bar set up would make for a more relaxed posture.
Distance riding on a 36er without handle bars may cause pressure on the neck because without them you tend to stoop your neck more as you ride.
If you’re riding without handle bars then at least try resting your hands on the front grip handle to take some of the pressure off your neck and shoulders.
I’d recommend doing shorter rides until you get get more comfortable with the bigger wheel. As a newbie to the big wheel you might feel a bit tense at first, but you’ll relax more as you get used to the extra height and speed.
When I first started my 36er I felt a bit nervous and would stoop over as rode. 
It was much later that I got to attach the handle bars. I practised using them on 24" before putting them on my 36er.
Hope this helps 
I’m sure your therapy will go well and you will be riding again soon.
Too bad. It is always hard to be forced not to ride. I am sure that your PT can even include unicycling in your weekly exercises to get a positive muscular reinforcement.
If you focusing well on your PT sessions and follow up, you will be back on the saddle in no time and stronger than before 
@unibokk: Yes, I have the KH T-Bar on my 36. Posture is something I’ve been trying to perfect since I got it, and I’ve definitely had to adjust since I started. My doctor’s theory is that my injury never fully healed, and overexertion didn’t help either
@Lou & Sidd: Thanks! Physical therapy starts Thursday.
Major bummer!
I hope you are on track to complete healing so you can rock inroad & offroad with your unis next spring.
(Note: I got your PM but there seems to be a problem sending you PMs. I arrived and waiting for my unis 
).