[noiv]

I wonder, whether there's anything interesting on the tape after a BB(5/6) halts?

[fwip]

You can read about the BB5 winner here - it looks like the final tape state is 4,098 ones in a row:

https://bbchallenge.org/1RB1LC_1RC1RB_1RD0LE_1LA1LD_1RZ0LA?w...

https://wiki.bbchallenge.org/wiki/5-state_busy_beaver_winner