Here's my take on pintle risers -
Take a stock height civvy truck with a stock hitch. You want to tow an M1101 level. So you fabricate a custom pintle riser. It looks like a steel plate, with triangular gussets, leading to a 2x2" drawbar that inserts into the stock 2" receiver hitch. To be level, you added about 11" of "up".
Now think about forward and rearward forces acting on it. It is now much higher than the 2" receiver. As viewed from the passenger side of the truck, acceleration will place counterclockwise twisting forces on the hitch, while braking will place clockwise twisting forces. The force is multiplied by the amount of riser.
So let's chop off the lunette ring and alter the trailer instead. The twisting forces are now applied to your fab work on the trailer. Worse than that, the plunger for the surge brakes is no longer pushed straight back but is twisted back and down and will act funny and bind, causing delays in brake application.
I used a civvy truck as my example because it has a hitch receiver instead of a bolted on pintle hook. The problems will be very similar with any alteration you come up with for the M1009.
A bigger player is the towed weight rating of the M1009. 1200 lbs I believe. The M1101 is 1480lbs empty.... you may want to consider an M101.
I hope this helps.
