Slam and Shield Rush rules broken!

[Bibiribobiri]

As commented on Thread "Shield Slam rules in GURPS 4e - problems?" the Slam rules seems broken:

Originally Posted by Lupo

The debate about how "effective speed for slams" should be calculated seems like a pointless exercise, since you'll end up doing either 1d-2 or 1d-1 damage anyway... extra detail is useless when the approximation is so rough.

The problem of slam rules isn't the velocity, it's that huge differences of ST and speed will result in tiny differences of damage.
The huge bonuses from AoA, shield slam and so on, only worsen the situation because they make ST almost meaningless: for example a ST 7 boy slamming with a large shield will probably knock down a ST 30 giant (1d vs 1d-1 if the collision speed is 3 y/s); if the boy were all-out attacking even a ST 49, thirty-feet tall monster would be in trouble (1d+2 vs 1d at 3 y/s).

Also, once you get in the "minimum damage zone" (HP x velocity less than 25), if your foe is stronger than you, the slower you slam, the better off you are, because you'll always do at least 1d-3, and reducing speed you will reduce your enemy's damage. In a collision at 1 y/s the aforementioned giant will need HP 150 or more to deal more slam damage than a shield-bearing kid...

Thinking of it the slam damage is probably the worst Murphy Rule of 4e!

Does anyone propose some house rules for a shield rush that are more realistic and ST sensitive (for an Fantasy game)?
How would the new shield rush deal with defenses or the wait manouver?