I fly off of grass too and I have ripped out more than one retract in my day.

So I bought some RoboStruts. I've used them on several review planes lately and I'm pretty impressed. They're not cheap ($40 each) but I do believe they will provide the extra shock absorbsion I'll need.

And don't worry about weight. The Ultra Sport is one of those planes that flies better with a little bulk behind it. That's why I'm not afraid to fully sheet the wing.