These are the ones I built from a guy on Greenhulk and they are killer. Harbor freight castors never had a problem and I have a rough driveway out of my shop. I even had a GTXL on one for months. Just google the twinturbostangs bomb proof stands.
These don't take all day to build. Metal ones are nice, but for what Suke paid that is another ski for me, I gotta invest wisely. I also modded on to be slammed on the ground. The height TTS gives works perfect for my trailer height, adjust accordingly.
Before you even comment Suke........NO, some day I will finish it.
Slammed edition
Full height to TTS's dimensions.