*update - there has been an update since I made this post, this may have been fixed but I have not had a chance to check*
This achievement is near impossible to do.
I ended up getting it using my turbo to spam
(5 ms on 5 ms off) to get slightly faster than normal speed. I cannot confirm this is possible without using a script, but I think it is.
After about 3 hours of trial and error I managed to get over 1700 five times (one time was right at 1795
My method was to put a sheep cow at the sign post in front of the barrier, back up to get a running start, and just as you go over the cow, grab and go down just a tad. It took forever to perfect but if you can get over 1650 with this method at least once, you should be able to get 1800 with a few tweaks.
Regardless of what ever method you use, this is going to be hard. 95% of my throws were under 1600. You also have to hope for the cow to land perfectly, if it hits at the wrong angle, the cow just eats the floor and you potentially lose 200 points.
Sorry, this Game Clip has been removed