Paulo Abreu
1000+ Head-Fier
... I prefer the JVCs, but they would slide off the tube too easily, either getting lost somewhere, or still in my ear. ...
Seriously, try cutting a 3 mm ring from a foam tip (a smaller size you don't use) and push it thru the JVC inside the umbrella, like I did it here:
http://www.head-fi.org/t/765867/jh-audio-angie-impressions-and-discussion-thread/2640#post_13324114
No more slide off and greater isolation and fit - give it a try...