Yes, very interesting and following all the reports, very much appreciated Will!
I do not think they are right about lowering the dipole for a few reasons: firstly NVIS is not as prevalent on 30m as it is on 40m, and secondly at the height of 23 feet it is already still optimal for NVIS. Lowering it won't improve NVIS to any noticeable degree even when possible but will degrade F layer distance significantly. Where you have it now is a sweet spot for both NVIS (when possible) and also for short F hop into Europe.
To make it good for DX it really needs to be up move than 10m, and even 15m. Then however you will lose NVIS. As that may be difficult to do, I think a vertical is worth trying!
If you try a vertical, if it is elevated above ground, I think this is better for a few reasons: one you don't need huge number of radials, just 3 (or 4) will be fine, those radials must not be on the ground. So long as the base of the Ground Plane vertical is less than 7.5m above ground, it will have low angle take-off for DX, but if you raise it higher than that you'll lose the low angle take-off, counter intuitive as this may seem, it is because it needs to be less than one quarter wavelength above ground as it uses the ground to achieve that property.
It's not worth trying to go a 5/8 vertical versus the 1/4 wave ground plane vertical in my opinion, as the difference would be negligible. The 1/4 wave ground plane is so easy to make. The potential downsides to watch for are noise: it will pick up any noise several houses even a block away from where you are, so hopefully you are in a low noise area. Also, if you have lots of obstructions around, so that low take off is not going somewhere near the horizon.
A ground plane is not an exclusive low angle DX antenna either: it will also have a nice higher angle lobe which will give you great results into Europe again.
If you do find that it picks up too much noise, a few pointers: first, let us not forget, and I know this from experience as does anyone who ever operated during a major power cut or from a remote location, then most signals are going to be hidden from you. It is amazing what you can hear when there is low noise level. And imagine some of those signals will also have a very low noise level so you can have QSO that would be impossible, with just S1.
So, if you do have any noise, and certainly above S3 (not on the meter, which is notoriously inaccurate and insensitive on even the most expensive rigs except perhaps the flex, VU2nsb.com search for noise and also search for S meter accuracy, he has great and well informed articles on these subjects), then you'll want to consider how to get rid of that noise.
Let's also not forget that getting rid of the noise is for your receiver, so for example, if your rig has a separate output for RX antenna (when it does there is usually a jumper there when it is not in use so that the TX SO-239 or whatever socket is used for both RX and TX) then you could think of attaching a low horizontal loop antenna, for receive. "DXCommander" has experimented with this to great effect, he may have a video on it.
And/or you need to locate the source(s) of the noise. Easy first step is power your radio off batteries and pull the mains switch. If there's any difference, you need to find what it is in your house, causing the problem. If not, it is outside your house, and you can try to track it down with a portable receiver. But when you have both the vertical (GP) up and your dipole, see if noise is worse on one or the other. If it is worse on the GP, then trying a separate (horizontal?) loop (? I also need to do more research on this, but certainly loops are good) just for receive, it may not even need to be resonant: signals may be weaker, but if there is no noise then turn on PRE-AMP and wind up the volume, it may be a great solution.
I'm not saying every vertical will be noisy, but the chances are generally higher, especially if you are not in a rural area. And it could vary a lot depending on who, where switches on what appliances.