I love these discussions, always a lot of ideas about licenses. Here is what the Feds say, local and state laws may vary.
Class A: Any combination over 26,000, provided the trailer does excede 10,000.
15,000 truck + 15,000 trailer= Class A
Class B: Any single or combination that excedes 26,000, but trailer does not excede 10,000.
80,000 truck + 10,000 trailer = Class B
Class C: Hazmat, tank or bus, under 26,000
Honda Civic + Hazmat = Class C
Class D: Any single or combination that does not excede 26,000
12,000 truck + 14,000 trailer = Class D
Unless your state's law says otherwise, a 25,999 truck plus a wood splitter is a Class B. All of the line clearence driver I have spoken to are required to have a Class B for their under CDL bucket truck with chipper.
Dave