The Munshine VIII was very useful while constructing my interplanetary ships. It hauled everything but the propulsion stage (hab modules, MPCVs, power modules, and payloads).
@Ampsterman: You should put the control surfaces on backwards so they work while you're landing. Like this: Just kidding! I like the way yours look more.
The maximum capacity of the Munshine-like LVs usually depends on the second stage. even if the first stage is really powerful, the payload may not reach orbit if: 1. The second stage's TWR is too low and/or 2. The second stage does not have enough fuel.
The probe core is a dummy payload. Unfortunately, I can't fix the sound of the rocket. You'll have to turn the sound down until Squad fixes the sound (I don't think they will ). I'll be releasing the Delta III soon and it isn't nearly as annoying.