There is no engineering problem that I have ever heard of with a pintle hitch. The military uses them with few problems on and off road. The real question is: Is it convenient "ENOUGH" for your purposes? I will be taking delivery of a new 8x18 tandem axle trailer, probably Sat or Monday. I looked it over this PM. They knew I was anxious so when they had a minor temporary material shortage they made a substitution of 7 inch channel for side frame and tongue where they would have used 6 inch. I'm not complaining, or worrying about the tongue! They recomended (and I took their recommendation) that it be fitted with a "bulldog" hitch. Like you, when faced with the pintle, I had never used one so I had to ask questions. It uses a standard ball but the hitch on the trailer wraps around the ball horizontally instead of dropping onto it vertically. The hitch is rated for 10,500 lbs trailer weight (weight carrying, not weight distributing). This neccessitates buying a new ball as they recommended a 2 5/16 ball. If you should choose to replace the pintle with a ball, consider the 2 5/16 version as they are available in much higher ratings. It is relatively hard to find a 2 in ball rated above, say 7-7500 lbs (I found one rated at 8000). It is easy to find a 2 5/16 ball rated at various levels up to and including 30,000 lbs. My receiver hitch is rated for 14,000 lbs (class five, 2 1/2 inch draw bar rather than "standard 10,000 lb 2 inch). I will buy a 30,000 lb ball ($39.00) so it won't be the weak link. Getting anxious... trailer is ready for delivery except for tires (16 in load range E, the tire guy didn't bring them to the trailer company today so we wait...) Oh yeah, consider a Titan class 5 hitch rated at 14,000 lbs for extra peace of mind. Good luck to you!
Patrick
