Now, let's have a look at some options provided by surplus (the junk box respectively).
|CFL bulb transformer vs. surplus iron powder toroid|
So, what do we have, the CFL transformer countd 3:3:12 windings. Using the black and the white in series, that would be 6:12. This would be, in other words, be a fine 9:1 UnUn.
The T68-2 is provided with 12 bifilar windings. This would therefore make you average 4:1 UnUn. Obviously, those can also be 1:1 isolation transformer.
Both junk-box items are proven in ham-radio designs. I figure, I will experiment with both out of the box options. Additionally, I may possibly try a 6:1 UnUn, as in the BB6W/BB7V design. Staying at QRPP levels would even offer the change of trying the termination resistor used in the BB6W/BB7Vs.
Oh, I forgot, to get closer to the BB7V, I will add some additional Al-pipe to top of the 5.5m long 27MHz vertical.