I built a similar project for my 12 foot boat. Worked out well people always say "where did you get that"????
My suggestion is design with larger wheels, so you can over come the small rocks and imperfections along the way. If you decide I am wrong then better have muscle or patience.
Best of luck
ABLE

I see four more years of economic stagnation and high unemployment if Obama is reelected. He lies every time he opens his mouth. "The GREAT DECEIVER"! Scary prospect.Worst president EVER.
UPS HAS ROTTEN CUSTOMER SERVICE, THIS I HAVE EXPERIENCED