I did some alterations on my UMP/SE: I was not satisfied with thous triangles shoeing form behind the bag and the shoulder-strap was sliding along thous triangels too much. So my DH smoothed over the rests of the hardware he had to cut of (see first post) and I did something very bad to another TB-Product to get two O-Rings (would love to be able to by thouse on the parts-page too, just saying).
Here are the results of this modifications:
And some thoughts: As I mentioned above, due to the shape of the UMP you do not get the howl extra space to use except you lay things on top of each other.
And it does not sit (used in purse-mode) as well at my side as a Side Effect does. Meaning it is sloughing around more. It works out for me good enough to use it as a purse but I thought you might want to know this. On a side note: I tent to fix my SE and this UMP with a short Key-strap to my jeans so that it is not "all over the place" when I have a lot bending down to do (three Kids...).