Wow, two 10" extensions. Glad you let that slip out, otherwise *THAT* would have been the answer to your thread title...
Yeah, the solution is a ONE-PIECE extension.
As far as your receiver not being rated for an extension, that may be, but if you de-rate the capacity appropriately, it will be fine.
E-trailer recommends you de-rate your capacity by 50% regardless of the extension length. I call shenanigans on this one, because as an engineer I know that the force on the receiver is proportional to length. The shorter the extension, the less you have to de-rate the receiver. This has to be CYA on the part of E-trailer, but it does make it simple because you can still "legally" tow 50% of your receiver's capacity with that 20" extension.
