According the author of this video you should Say Goodbye to that G5RV! Look at the ZS6BKW. Here is his proof of concept.
Enjoy the video and let me know if you decide to take the plunge and build one.
I noticed a link on eHam.net to an in-depth technical article about this antenna, written by it's developer Brian Austin G0GSF (ex ZS6BKW). It's taken from a UK QRP magazine called
Sprat & starts part way down page 1.
https://www.nonstopsystems.com/radio/pdf-ant/ZS6BKW.pdf
He determined the optimum impedance for the parallel-line matching section of feedline is about 400 ohms. That's convenient as the actual impedance of the "450 ohm" window line you can buy is about 400 ohms.
Claimed performance is impressive for a no-ATU antenna:
band 40m 20m 17m 12m 10m
center freq. 7.1 14.2 18.1 24.9 28.97
min. SWR 1.1:1 1.1:1 1.3:1 1.4:1 1.4:1
2:1 BW (kHz) 360 270 380 260 400
73
Dave, VE3WI