probably not possible. But I have a limit on htlc of 8. Actually had. I'm not routing anymore... private channels only
Discussion
I only have private channels too. I've never routed. But I have seen 3-4 sat fees on 21 sats coming out of places like cashu mints, phoenix, and coinos. Phoenix might be price gouging me because I can only connect to their node out of the app.
It might be an accumulated fee.
I can imagine they do something similar to this: