Okay, I thought I's share this with every one that has purchased an Ultrasound 2.0 board that wants to use a tactile switch, but has an MHS based saber using a standard TCSS push button. This was a click-on/click-off type, but I'd guess the momentary is the same...I have one of those I'll look into to converting next.
The first thing to do is pry open the switch housing:

These are just press-fit together, so it should be a snap if you have a hobby knife like the one pictured.
Here's the switch dis-assembled:

The first thing you'll need to do is remove the wires. In this switch, there was a post in the center of a round hole that one of the wires was attached to. This post must be removed. Remove the wires by simply pulling them out. the post can be removed with the hobby knife, then once that is done, you'll need to carve out out enough room for the new tactile to fit:

All done:

Solder wires to the mini-tactile switch:

I got the mini tactile shown from here:
http://www.allelectronics.com/make-a-store/item/MPB-132/MINI-TACTILE-PUSHBUTTON/-/1.htmlIt has four solder legs on it, only two are required for this. Snip off the unused legs with a pair of diagonal cutting pliers.
The switch should fit in like so:
Take the plunger apart:

See the white piece? Toss it, it's not needed...that is part of the latching mechanism....Don't lose the spring! Next, re-assemble the plunger in this order:

The spring goes in first, followed by the copper piece:

Re-insert that assembly into the top half of the switch housing...we're almost done!
Begin re-assembly:

Be sure that the pins that hold the halves together do not interfere with your wires. You may have to use the knife or dremel to remove a couple to allow the wires to fit through the slots in the switch top piece. Line up the pins to their respective holes, and push together:

Congratulations, you now have a tactile switch to use with your Ultrasound 2.0 powered MHS saber!
* I have not yet tested this with a uS2.0, but will shortly and will modify this post with results.
EDIT:
It seems to work just fine....I did get kicked out of the menu once the first time I activated the board, but I've scrolled through the menu settings five times now, using all of the settings and haven't had any trouble since. It may actually work better without the spring, but then the plunger is loose....