Tvheadend

Hello, new user of tvheadend. Have three Xbox Digital Tuners connected to a Raspberry Pi running tvheadend. Everything is setup and running okay. I can stream individual channels from each tuner that has 5 multiplexes each. Would like to record a multiplex from each tuner and not individual channels. Am aware that the resulting transport stream file will be large. Is this possible and how? Thank you for your help.