It was recently brought to my attention that you can set up a game either for automatic handi, or for a specified number of stones, but that there is no option to set up a game with a maximum handicap.
With the multiple ranks, setting a rank restriction for automatic handi does not work as a workround for this, since someone with an overall rank inside the restriction can accept the game, but the handi will end up being set based on the rank gap for that game type.
Example: a 10 kyu sets a game with auto handi, rank restriction +/- 3. Challenger who is 12 kyu accepts game. 10 kyu player has a blitz rank of 9k, and 12 kyu player has a blitz rank of 14k, so the handi is set at 5 stones, and it becomes an easy game for the 12 kyu.
My suggestion is to add an option to the game creation window that lets you set a max handi but automatically sets the handi based on rank difference if the rank spread should result in a handi below the maximum.