What a coincidence, I actually just got both
The suction base fits pretty well, but the dildo doesn't totally stand up on it's own. The balls, however, definitely do not fit in the hole provided in the Wing. For the most part, the Wing accommodates slimmer dildos, but most dildos with a flared base will fit under the fabric slits, but not in the actual hole provided.
Also, the John Holmes UR3 is REALLY big, so riding it on the Wing might be a challenge for just about anybody. I certainly don't have the guts to try it!
My advice is if you are looking to ride the Wing, then you should focus on finding slimmer dildos (approximately 1-2 inches in diameter) without balls.
Hope this helps!