Hey, that sounds familiar, lol!
I was going to originally make the second delay fixed and use just the 2nd manual control to set how many milliseconds the fixed delay is... But there was room on the Lectric FX PCB (each channel uses 2 of these PCBs) to add the second LFO so I just added it for versitality. I find that the best TZ effect can be had when both delay lines are swept by the same LFO and one delay line is set with the "range" knob fully CW and the other delay line has the "range" knob set about 1/4 to 1/2 way. I guess this would be the BBD equivalent of using two tape players to get flange effect.
I've added some other different LFO functions that's not on this schematic, as this is the only schematic on my phone.
The one caveat is that both BBDs need to have very close bias voltages as they are direct coupled to the op amp that feeds them. Not too hard to do if you have several MN3007s.
Here's the schematic for one channel. Both pics go end to end so the connections (letters - A, B, C, etc) line up.

