I discovered a stash of this film in 4x5 I did not know I had, and made some test shots at iso 100 w/o filter and iso 6 with a 720nm filter. Got really thin negatives with xtol stock replenished 30 sec agitation for 11 minutes at 73F. My normal time for Rollei 400 IR with the filter is 8 minutes at that temp. I am thinking xtol does not like Efke. How about Rodinal?? Any experience with Efke??