Mandatory Slide Rule

One of the local rules we're looking into this year is the so-called "mandatory slide" rule. Most rules are more-or-less worded that an offensive player cannot interfere with a defensive player, but there is a wide range that this can encompass.

We didn't really have a problem with this until our kids got into All-Stars. At a game in another town (which is infamous in this area), our runner crossed home standing up, but was called out because the ball was in flight to the catcher WHO WAS STANDING ON THE INFIELD GRASS. No, I'm not kidding. It's par for the course with that league. I'm just surprised they didn't eject our runner at the same time.

Anyhow, I'd like to create a tougher "mandatory slide" rule because (A) it's safer, especially for the kids in the minors, and (B) talking with others, it seems this is a growing concern.

Any suggestions as to how strict to make it (or if we should make it at all)? Any assistance on how the rule should be worded would also be greatly appreciated.