Instead of Rank, I exclusively use RankPos in the sell rules and see no problems doing so. For me, it seems natural to use a count like ranking threshold when the number of positions is fixed; a 20 position portfolio will have a RankPos somewhere over 20. I’m not sure what the issue is with slippage and weekly rebalance + rankpos. My models tend to have transactions with a high average return and long holding periods.
Walter