Bidirectional Behringer C-1?

Hi there, first post in a loooong time...

I bought the other day a Behringer C-1 at a Hamfest... I don't know what took me, as I have a fair number of good microphones.
In its present state, it is of not much interest. I am, however, a big fan of bidirectional (figure-8) microphones. I could have more.  It crossed my mind: could I convert this mic to Bidirectional??
Now this capsule is not even a condenser, but an electret. I know a bidirectional capsule's diaphragm is free in the back and in the front. From the picture attached (back of the capsule), the back seems at least partially free (a few holes). I guess the black plactic surround with holes contribute to the directionnal pattern.... what if I just ripped that?
This question is obviously aimed at people with knowledge of capsules, particularly electret. Could this capsule be converted to bidirectional? how? should I drill more holes in the " backplate"? what happens if I unscrew that little bolt?

thanks,
P.O.

It looks like the same capsule as used in the Behringer C3.
The C3 uses two electret capsules back-to-back to obtain a bidirectional pattern.
IMHO those capsules are low-quality.  They are lacking LF.
The Behringer C3 is without doubt the worst microphone I ever had...
(Not speaking about the extremely high noise level!)
More HERE

Yes, I have read about the dreadful C3... Fortunately, the C-1 is not as bad, and the electronics are very different.
But my aim is really to understand better the mechanics of a bidirectional condenser capsule... I know a little about the Sennheiser MKH30, but it seems all the others achive a bidirectional by combining two capsules. Couldn't you achieve a bidirectional condenser if the backplate was open enough?
Ribbons are bidirectional devices, and they are mechanically pretty simple...
How does the mechanically-switched pattern Schoeps capsule achieve bidirectional?

The only thing I could think of, is that you would need an 'acoustic transparent' backplate.
In that case you could use a single membrane.
But...that would in reality mean: no backplate at all!
All microphone manufacturers (I know of) use a capsule with a front and back membrane to obtain a bidirectional pattern.
No idea how you could do this with mechanical switching.
I have seen mechanical switchable patterns between cardioid and omni, but this is much easier.
(Pressure gradient or pressure receiver.)

What I was thinking about is the Schoeps MK6 capsule which achieves omni, cardioid and bidirectional patters with a single membrane. Same as the CMTS 501, which I have. I found some mechanical diagrams of the capsule, will study that. I guess it would be easier to convert my C-1 to omni...

It seems there is an article on the construction of a bidirectionnal capsule on the micbuilders group...
I created a Yahoo account yesterday, and tried (and tried) to join the group, to no avail.
Yahoo groups appear to ba a real disaster, lots of people complaining, and Yahoo remaining inaccessible and offering no solution whatsoever. Has any of you had success trying to join this group?
Would anyone be kind enough to post this article or to email it to me?
Thanks