Sorry I have not responded. Did not get an email notice for some reason.
Yes, I did consider cutting slots in the tail rack, I may do that yet. But my impression is that keeping it wide makes the strap more verticle going to the bag. This looks like it will put less stress on the strap where it attaches to bag. The straps around the body of the bag hold it nice in snug. I don't think it will be flopping around at all. The straps across the seat only hold the verticle weight. So keeping the straps as verticle as possible looks like the best way to hold that load. Time will tell.
Info from Wolfman site :
Length: 16" / 41cm top, 15" / 38cm bottom
• Width: 10.5" / 27cm top, 8" / 20cm bottom
• Height: 13"-16" / 33cm-41cm depending on amount of roll
Capacity: • 32 liters / 1950 cu. in. each, 64 liters / 3900 cu. in. for the pair
• 3 additional liters available by reducing the amount of top roll
http://www.wolfmanluggage.com/index.cfm?fuseaction=product.display&product_id=312