Chip...while I'm not certain, I think the single suppliment for Penthouse cabins is pretty high.
The normal suite should be very comfortable for one person and on many cruises the Radisson suppliment is a bargain compared to other cruiselines' pricing. On some itineraries it's only $99!
Of course each cruise is different, but if you're traveling solo, shopping for those $99 (single suppliment) rates would be worthwhile!
