Hi, For those That want to know more about “Double wheel extension”

Go to your Hardware store (the biggest is the best, you will not have to run around the town.)
Bring your buggy hex hub with you.
In the pluming area try to find threaded union that will fit tight on the thread part of the hex hub. (the thread will not be the same but the first thread should engage.) When you have your union, go in the lamp area and get the full threaded extension tube that will fit the union thread. (the union thread is taper so its normal if you can not fully insert the tube in. While you there get the nuts that fit on the threaded tube (the original nut of the buggy will not be required any more.

At home , put red lock tight on the inside thread of the union and engage the tread of the hex hub into the union. (you can force “wedge” the to parts into each other with a vice). Be sure that the union and the hex hub flange are mating perfectly. Let it dry for the night. Cut the extension tube in half and drive it into the union as far as possible (do not forget to put the red lock tight before) Temporary use the nuts and lock 2 nuts to getter on the threaded extension to help tight the extension in to the union if required (so you will not damage the thread of the extension. Put the nuts you bought in to the inside wheel and screw the wheel on the threaded extension. (my tube is a little bigger than the wheel hole, so help it by applying pressure on the wheel , it will make is own thread path in the wheel hole and self center) . Put the other nut into the other wheel and drive it like the first wheel. If you did it right, you should only have to turn the outside wheel until the 2 tires rim mate. Apply reasonable torque. Use your feeling , you will never break the thread but you can distorted the wheels and it can break if you do not have full cover wheel.

Check the photo, and try to inspire your self with it.
http://www.youtube.com/watch?v=P1bFK-l0VQ4
http://www.youtube.com/watch?v=sIB6jLtTs0k
I do not put dimensions because all buggy have there own spec.

Take time to look and ask help to the hardware store employs for similar parts.

The original hex hub will not be usable after they will be wedge into the union, (its good to have spare one).
See Yaa!
Frank_514