As you can read from my quite long answer to Marconi, the added wires are 17 to 18 feet long, 5+ meters long, just a bit longer as 1/4 wave at the lowest used frequency at 18 MHz.
The choke is 2 x type 43 material large clamp on ferrite's that were at the junkbox at the time, don't think they do a lo there.
What I did find was that the Imax was quite sensitive without any ground wires getting close to the antenna set off the swr quite easy and shifted the resonating point.
Adding the GPK kit from Imax changed that for the higher bands since most measurements were done at the antenna base with a short jumper and a MFJ 269 antenna analyser measuring directly at the antenna.
The added long wires also took care of 21 and 18 MHz bands, removing the sensitivity to near objects shifting the swr and resonating points.
I clamped on the ferrites just to be sure and they were in the junkbox anyway 
Can't put up beams here, already the roof here looks like Jodrell bank with all the antenna's up here.
Living here for the last 28 years I made the best of what I have to work with, and it suits me well, I can run the amplifier here without getting my neighbours at the front door with pitchforks demanding ceasing transmitting
I never look for an easy way out, hence my 160 meter obsession, why take the easy road if there is a challenge?
When I started with 160 meters every ham here told me it would not work in the city, and yes there are challenges to overcome, but I did that.
Just another reason I work in Phone and not digital or CW.
Would be quite easy to work the world on 160 digital modes or CW, but where is the challenge?.
Must be the reason I use the Desert Eagle in .357 Magnum to do most of my target practice in our gunclub, and beat the sh*t out of the guy's with their nifty tuned and prepped 9 mm target pistols
After winning all trophy's with the S&W 629 classic DX .44 Magnum revolver I sold that one off, no challenges left there.
When they tell me it cannot be done I will do try to find a way to get it done.
