It's not really a ratio imo. You want at least 20 more agility than the best linemen you'll face, 30 more on average. You need 75 to 80 speed total. And you want minimum 80 strength, or you want to be within 25 or 20 strength of most of the guards you'll line up against. If you figure most guards will be 110 strength and 75 agility, you want 85 strength and 105 agility to be moderately effective, anything more than that will hep you be a standout type player, or effective in the highest leagues.