The hip belts should mount to the lower bars of the rollcage, not the seat itself, since the hip and shoulder straps absorb the majority of the energy in an impact. The inner leg straps are only a supplemental system.
Here, you can see how the shoulder straps attach to the bar, approximately level with the top of the driver's shoulders. This is the best angle to keep a driver's shoulders from sliding forward or down in the event of an impact.
Another view showing how the inner leg straps (red) are located in the race seat in comparison to the antisubmarine belt.
Losito uses a HANS Device. After entering the car and making himself comfortable in the Butler Built aluminum racing seat, he slides the HANS Device over his shoulders (he's able to put his helmet on inside the car) and positions the shoulder straps over the HANS.
The hip straps are the first to be buckled into place. In addition to the seven-point belt system, Losito is also experimenting with a cam-buckle system for 2007 instead of the traditional latch.
The inner leg straps wrap across the inside of each leg, then run through a ring on the hip belt before sliding the loop on the end of each strap over the buckle on the end of each shoulder strap.
Since the inner leg strap slides over the buckle of the shoulder strap, when the shoulder strap is buckled into position, the leg strap is, too. Lastly, the antisubmarine strap is clicked into place on the cam lock. Losito tightens all the belts down, straps on his helmet, and is ready to race.