Your Trip and duty rigs are factored into your pay credit for the trip. For a very brief desciption of various rigs, visit here, under subtitle "Duty and Trip Rigs"

For example, a 20 hour block 4-day. TAFB for the entire trip ends up being 80 hours.

Day 1:
Block: 2 hours
Min day pay: 4 hours (or whatever it is)
Pay: 4 hours

Day 2:
Block: 6 hours
Pay: 6 hours

Day 3:
Block: 5 hours
Pay: 5 hours

Day 4:
Block: 5 hours
Pay: 5 hours

Total Block time: 18 hours
Total Pay credit time: 20 hours
TAFB Trip rig (3.75:1): 21:20

Pay = highest of them, or 21:20 for the 4-day.

Hope that makes sense.

What you'll probably find now is slightly more productive trips, and that rigs won't really have an effect on your soft time. This is because they encourage the company to make more productive trips otherwise they pay you to do nothing.