Just something to keep in mind, and mull over. It's something most people, game designers included, underestimate, and that is the concept of attack density. The more attacks you're compressing into a given time frame, the better off you are unless the accuracy penalty is very detrimental...more than most games impose.
Even with nearly any penalty you choose, going from the 4 person baseline that 3e was developed with to 6 people, you've increased by 50% the number of attacks per round the party brings to bear...50% more chances to roll that 20...lots of extra flanking potential...more people left with openings when "per round" type defenses are overwhelmed. A well played group is more than the sum of its parts, and the sum increases more quickly for every extra person you add.
Take whatever formulas the designers give you for determing the ECL, toss'em out and start experimenting...only trial and error will show you the sweet spot to challenge them. To echo others here though, the best counter to attack density is opposing density, not more power. Send in more opponents, not tougher ones.
Even with nearly any penalty you choose, going from the 4 person baseline that 3e was developed with to 6 people, you've increased by 50% the number of attacks per round the party brings to bear...50% more chances to roll that 20...lots of extra flanking potential...more people left with openings when "per round" type defenses are overwhelmed. A well played group is more than the sum of its parts, and the sum increases more quickly for every extra person you add.
Take whatever formulas the designers give you for determing the ECL, toss'em out and start experimenting...only trial and error will show you the sweet spot to challenge them. To echo others here though, the best counter to attack density is opposing density, not more power. Send in more opponents, not tougher ones.