How many extension cords can you string together?

If it were me, I would purchase 50 feet of 6 gauge, 3 wire cord and add 30 amp ends to it. You will not have near the power loss as with standard 10 gauge 30 amp cord and the price should not be that different than purchasing a ready made cord. In all my wiring, whether in out old TTs or in our S&B I always go with the next size bigger wire (next number size smaller), the price difference is worth the piece of mind I get from knowing I have ample capacity.