Just received the Edwin Jagger head for my CooncatBob Bull Mastiff Stubby UL handle. I'll post some better photos and a review after I get a chance to use it. The balance feels great in my hand, I'm still deciding on a heavier nob to make the handle heavier.
After a few shaves with the Bull Mastiff Stubby UL, I am really happy with it. I might order the heavier nickel end nob just to have it, but I have no complaints with the current weight. It really feels great in my hand and doesn't slip at all. I definitely have a lot of control over the angle of the head. Cosmetically, it's the nicest handle I have seen.
The Edwin Jagger head is great. Finished very well, and not overly aggressive. It has some really well placed "channels" to rinse the back of the razor blade. I also like the way the 3 knob system holds the blade in and stays flush within the head.
The stubby is just a little shorter than my Merkur HD (as you can tell from the pictures). It's definitely lighter, but I haven't had a chance to put them both on the scale yet. Loading is a bit trickier with the Bull Mastiff 3 piece than it is on the 2 piece HD, but nothing too terrible.
All in all a great razor combo, and I like having something a little different. Here's some comparison pictures next to my Merkur HD: