Tournament Jousting

The Gygax & Perren Chainmail Man-to-Man Combat rules (I'm looking at 3rd Edition, 7th printing, April 1979) culminate with a short section on Jousting between knights in a tournament. It's only about four paragraphs, and most of the action is offloaded into a table in the Appendix, as shown below:

Again: Pretty cool. As you can see, the action is decided in a matrix comparing each rider's choice of "aiming point" (column on the left) to "defensive position" (row across the top). I generally like these kinds of mini-games if they're well done, and clearly this gives a very concrete result to the proceedings, so I'd like to use it. However: The system pre-dates the whole concept of levels in D&D, so it fails to incorporate any differences between competitors for fighter level, proficiency adjustments, ability scores, or anything else. Also, I think the allowed defensive positions rule is kind of complicated for players in practice, and I must say that I find the presented scoring system (p. 27) hard to decipher.

A Second Go

Let's consider making a few marginal modifications to this system. First, I'll ignore the "PDP/AP - Possible Defensive Positions Considering Aiming Point", and for simplicity say that players can choose any defensive position they want at any time. (While probably more realistic, this complication doesn't quite seem to fit the "where it does not interfere with the flow of the game" golden rule for realism concerns).

Second, that a result of "U - Unhorsed", which would normally win the joust, simply indicates a possible unhorsed result, that must then be confirmed with an attack roll by the jouster in question. Roll d20 + attack bonuses (level, specialization, Strength, any magic, etc.), and if the total is 20 or more (effectively target AC 0), then the opponent is actually unhorsed and the joust is over.  (A failure to confirm means that the attacker didn't quite succeed at the aiming point, or flinched at the last moment, etc.) This then brings in different D&D attack abilities to secure the win, while keeping the overall flavor of the original system. If an "I - Injured" result is seen, then roll lance damage normally with Strength and other modifiers included (not double damage -- these are competition lances with blunt ends and so forth).

As far as scoring goes, I'll say the same thing that Gygax does (p. 27). Competitors get three "rides" and if one is unhorsed, then the joust is over at that point. Award points of +3 if you knock the opponent's helm off, or +20 if you unhorse them. Subtract -1 if you break your lance or -10 if you get injured. And lay on!

Questions:The Gygaxian joust scoring seems unclear, do you read that differently than I do? Or do you know of other joust scoring systems that seem more suitable?