Joe, I only bowled one league with a 10 pin drop rule and the way it was used was for entering average team caps only. For example, I had booked 188 one year, the next year I booked 167. Since my average had gone more than 10 pins down, I was brought in at a 178. It had nothing to do with anythig except determining if we fit under the cap.
I have never bowled in a league that used the 10 pin drop in any other way. It seems to present interesting questions.
USBC Rule 105e An absentee score is to be used when a member is absent and a substitute is not available. The following provisions apply unless otherwise provided by a league rule:
1. The absentee score for each game shall be the absent member's current average less 10 pins. In handicap leagues, the handicap shall be based on the absent member's current average.
I'm glad we don't have to deal with the situation
Good luck!
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"I cannot change the direction of the wind but I can adjust my sails to reach my destination." Jimmy Dean