Time trial saddle bag modification

Modified Saddle Bag for Time Trials

This is my low-drag saddle bag modification that I use on my time trial bike.

I need to have a saddle bag for my local evening 10-mile time trials, which start 5-10 miles away from my house, to carry a spare tube and some basic tools.  I don't have pockets in my skinsuit unfortunately.

The standard Topeak ProPack saddle bag, shown in the photo below, sits below the saddle, in the wind.  It always irked me that the nicely aero-profiled seatpost on my TT bike was spoiled by a large lump of a saddle bag sitting directly behind it.

Original Unmodified Topeak Saddle Bag

Now, with the extension I made for the saddle bag, using some timber offcuts, it should be lower drag.  It doesn't change the drag coefficient of the saddle bag, of course, but it now sits in the wake of my backside, so the dynamic pressure and the resulting drag (in Newtons) should now be lower than in its original position. 

I later modified it further, to have a red light on the back too, to comply with CTT regulations requiring a rear light.