Rules Update

I've been spending time today researching the potential impacts of transitioning my game to the C&C rules. Since I found one or two things that might be detrimental to the existing characters, I've decided I need to discuss Castles & Crusades with my players in more detail before making a switch. In the interim, I'm considering the following changes to 1e/OSRIC:

• Upward AC. PC base to-hits would equal 20 - THAC0. Monster to-hits could then equal their hit dice. Calculating AC is trivial: just add to (instead of subtract from) the base of 10. Doing this math up front should make attack rolls much simpler, with no ill effects, and eliminate "to-hit" tables.
• "SIEGE" checks for task resolution. This would replace AD&D ability checks (or the lack thereof) and saving throws with a standard "d20 + modifiers vs. target DC" mechanic. This is the meat-and-potatoes of Castles & Crusades, and seemingly makes task resolution a breeze. No more wondering what to roll, or if you want a high or low result. Of course, a great complement to the SIEGE system is...
• Standard ability score bonuses. 13-15 = +1; 16-17 = +2; 18-19 = +3. This makes mid-range scores more relevant, and bonus thresholds easier to remember.

For next session, I'll likely implement only #1 (which is purely a syntactical change), and continue to use d20 vs. ability score for ability-based checks.

I also want to develop and print a "cheat sheet" of rolls for my players. For example:

• Attack roll (high) = d20 + modifiers vs. AC
• Ability check (low) = d20, less than or equal to ability score
• Saving throw (high) = d20, greater than or equal to saving throw value
  
• Initiative (high) = d6, result determines combat segment on which opponents act
• d% (low) = d10 for tens digit, d10 for ones digit; succeed by rolling less than or equal to a target percentage; "00" = 100

That's all for now.