more splitter isolation transformer questions

[blackieNYC]

 I wish to make a ground isolator.  I figure I'll make it like the Geofex with a couple exceptions.  From Geofex:
I have a stereo setup in mind, and it's been my experience, like most I'm sure, that the other amp on the other side of the room is going to give you ground problems (best solved without lifting the 120VAC ground plug). I have plenty of stereo effects at the end of the chain that I won't actually need a splitter, so I'm thinking of a single channel isolator like ISO 1 or 2 above.  I have an Edcor 10k:10K big chunk of iron.
1. the op amp driving the transformer above looks like the output stage of all my pedals.  Given that I am not using the little TM018 (which works great in the above circuit), could I just skip the active circuit above and rely on the output of my end-of-chain op-amp buffered pedals to drive the transformer?  Even in a TB pedal chain, I always have some thing on - isn't it likely that any pedal I have could drive this isolator just as well?  Seems OK in my limited bench-test setup.
2. How about my Ge booster? (100K voltage divider output volume pot) I don't have the schematic for it anymore but it's nothing unusual.
3. If its OK to drive it with a pedal, I may wish to put the transformer in a metal box (properly isolated output jack) velcroed into the back for the amplifier.  So 15-20 feet of cable would precede it after the last active pedal.  Foresee any problems?
4. I like the LP filter in the spotter schematic.  On the bench, with a mess of clip leads, the edcor transformer seems to have a rather extended bass response that increases gain by 3 dB or so as I sweep a buffered test tone down below 80 Hz.  I'm certain to have a pedal on that filters out the low lows, but I tried a bit of RC filtering at the input to the transformer and not surprisingly I found the results to be incoherent - I'm smart enough to guess the transformer factors into the filter, but the smarts stop there.  Maybe it's not worth doing, but if I wanted to roll off lows below the guitar, or perhaps bass, range, how could I do that?

[PRR]

The front-end shown has gain of 2.1. I know about the 0.1, but am not sure why the 2.

To smack the transformers good you want source resistance well under 100 Ohms. Yes, many opamps with small series resistors do this fine. Discrete transistor schemes mostly won't. Opamp schemes often tack assorted resistors and controls between the opamp and jack. Do you really want to keep ALL that in mind when setting up and selecting sounds?

Good stage audio interfacing can be a lot about not burdening the player with impedance considerations when he/she should be buttering-up the audience. Or punching to a "killer effect" which comes through like a cheap transistor radio.