Hi there HH,
I have osteo in my right shoulder and had my main front right neck muscle removed a few years back, this means I really struggle to swing the gpx4500 with one arm for any longer than 1 hr, I also struggle with poking the coil between scrub, so I got a swing arm (pictured) and have never looked back.
I can comfortably swing for 3-4 hrs no problem as my arms are sharing 50/50 push/pull, it also means you get so much more strength to push the coil between those pesky grassy clumps and detecting inclines or sides of slopes etc is so much easier. My osteo in the shoulder joint doesn't play up at all and I wouldn't swing the gpx without it.
When using a bigger coil it also gives you so much more control over your swing, well worth the money.
I was talking to someone the other day about the swing arm and they had the straight handle like the one you pictured and they didn't like it as they said it was difficult to hang onto. I find mine real easy to hang onto and my only wish is that it was slightly longer so I could put the mount knuckle lower on the shaft for even more control, I'm working on modifying the length.
I know GSA in Dunnolly used to sell them, there's one for Minelab and one for Whites machines, mine was for my TDI SL when I had it and the only difference is a thin clear sleeve inside the mounting knuckle, I removed the sleeve so it would fit the gpx as the gpx shaft is about 2mm (thereabouts) bigger in diam. so if you decide to get one of these swing arms don't be fussed which one you get as they are exactly the same apart from that sleeve.
Hope this helps.
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