Remember making the gp from the chart on pcs website, put in the loft it worked, many seem to have good results with it and are suprized by it, fed from the bottom with 50ohm coax, the perfect match. Good for keeping the hills alive with the sound of music, good when you’ve got ground which is higher

I've used these fibre glass telescopic poles before but I have the "SpiderBeam" variant which is more or less identical I guess, however I never thought to use it in the way this guy has; I've only ever used them for EFW on MW and HF, typically with a air wound loading coil at the base on a PVC waste pipe. I did share this on the RN forum some time ago. I later used a toroidal FT 250-2 core with much success and made a simpler and easer installation.

I guess this would be ideal for a pop-up weekend station transmitting from a high wooded area.

I've used a 12m fiberglass mast up a very big hill for some long weekend stations in the past few years. Was surprisingly stable even in the wind, the whole mast would flex but it wouldn't topple over. Although I did have the telescoping sections collapse in on themselves once overnight, which took the station off air. Seems when rainwater gets in between the sections it lubes up the joints and lets the whole thing telescope down, I suspect once one section goes the others go with it.

Originally it had an end-fed flowerpot using RG58 duct-taped to the side, but I could never get it to match better than 1.5:1 and the coverage was patchy. Later I changed to a ladder line slim jim also taped to the side. That matched easier and gave much better coverage. Running 100W I got good coverage over about 35 miles and furthest reception was 65 miles away up another big hill.

Right now I have a 1/4wave GPA in the loft made from alu tube with the legs just sitting on the floorboards. After some trimming and bending the legs it matches almost perfect to 1.05:1, although moving it at all makes it go out of tune because the alu sheet I used for the centre piece is too thin for the weight of the elements, so the legs flex a lot. I run half a watt into it usually and get full quieting stereo coverage >1 mile away and patchy out to 3-4 miles. Distance record for full quieting was 8 miles with the car radio parked on top of a nearby hill. Also occasionally run 50W and get out to ~20 miles. This is just from the loft of a 2-storey house maybe 10m ASL. I bet it would work great up the really big hill, probably too heavy for the fiberglass mast though.

In a previous property with a decent sized garden, I used a similar mast as a monopole with a #12 wire run up the inside and radials made from alu fence wire buried under the grass. Used on MW with a loading coil wound from #12 wire on a piece of plastic soil pipe, then tuned with an L network using a valve radio tuning cap. Tuned up nice but was very inefficient, only got a couple of miles of staticky coverage with 1W. Probably needed much more power to get anything useful out of it. Also tried winding the loading coil on a ferrite core but found it was too lossy with any ferrite mix that gave a realistic number of turns. It would give a really wideband match which barely changed even with the antenna disconnected, which I figure means all the power was going into the ferrite and not the antenna.

Same antenna worked really well on SW (without the loading coil). Was resonant just above 6.2MHz without any tuning needed. With 5W was picked up on an SDR about 140 miles away.

I do remember with the gp, relaying hooked on classics, not everyones cup of tea, never lost the signal went weak, on the hills, you think you’ve lost the signal its just a low part in the music, the stereo sign flicks back on, the music starts up again, classical music with a menotrome beat. On low frequency with a dipole the signal would often be lost you’d get a burst now again, never heard anything like it, still listen to that now, remember when you never lost the signal, the day it was heard everywhere.
Hard to believe it just worked from that chart, with wires taped to some paper tubes, like some epsoide of blue peter with shini, though top part had to 5-6cms shorter, that part was an alumium tube. it was just on top of an old poster tube in the loft, it fell down in the night, easy to repairfound some better way to put it up, the poster was of austria it did reach simliar scenery.
it was still rolled up paper tubes with just wire, barely 3w little tx, was my favourite one of all time, stereo all in, had rds too I turned it off I couldn’t think of a name. I did sometimes put the rds as another frequency, I found abit funny to do that, what mondo fun.

I suppose the gp is quite cute even with 3 legs, if the radials are made of wire outside I suppose bird might land on them, so I guess you'd have to straighten them out again.