Just looking at the design scares me away from that jack foot extension. The offset design builds in a side load that will push the trailer forward when you load the jack. Gotta chock it.
I will admit that I learned the hard way, with a flip foot extension.
Unless you are on a perfectly level surface ALWAYS CHOCK YOUR TRAILER!
I almost destroyed a jack and flip foot by not doing so. Lucky for me the truck was still there and all I did was dent my license plate and tweek the end of the jack pipe. Please for safeties sake, once you have it where you want it. Put chocks every where you can. Another reason I hate wheel blocks. you cant chock wheels up on leveling blocks. I put another pair of leveling jacks in front of my front axle for side leveling purposes. that way I can chock on both sides, most of the time.
Please take an extra step toward the safe side. RVs are for fun But can be a recipe for disaster.
Have a Safe and happy camping experience.
BB