I don't know what the gain figures are for UHF with the 741, but the similar HBU11 is around 5dB +/-, and the DB8e is around 10dB +/- with the two panels facing 180 degrees apart, so I would think that you could aim each panel towards the two clumps of transmitters and still get higher gain than you have now. Each panel is basically a DB4e (about 13dB gain +/-), but combined and facing away from each other as they did with the DB8e they have less, but still twice what a single 741 has. Combining two 741's into the same tuner would reduce the gain of both, I would think, so going with something professionally made for that purpose would seem to be the best solution. From where I sit, of course. Add the h-vhf antenna if you need it, as GUM suggested, aimed at 36 deg. magnetic, for the best of all worlds.
DB8e data sheet page 8
DB4e data sheet page 2
HBU11 data sheet