I have no idea whether an experiment like one you describe would show a difference. I think there is probably some kind of bottleneck in the data the retina sends to the brain, and I imagine that could stand in the way of testing my attention in the way you describe. But the basic point is interesting.

I could imagine lots of experiments which I believe would likely show a difference in perception and attention between people who meditate in the way I've described and people who don't. For example, I claimed that mode four perception has "wide attentional width". It seems likely that this implies that a person in that mode of perception would be much better at attentional tasks involving simultaneous recognition of objects in different parts of the visual field. (For example, imagine watching a large computer screen that flashes two images, at the far left and right sides simultaneously, and having to explicitly say something about what properties those images had.) And since I can get into mode four perception when I want to, I should be better at these tasks.

On the other hand, most low-level cognitive processes are inaccessible to introspection, so without any knowledge of cognitive psychology, I have no idea whether the feature of experience I call "wide attentional width" would translate into this particular finding, or not do so because of some detail about human cognition that cognitive psychologists know about but I don't.

So, ultimately, I expect that a variety of tests along these lines would find obvious differences, but I don't have enough knowledge to pick out any particular one.

Risto Saarelma mentions EEG readings, and I imagine that meditating in the way I describe would produce obvious effects there, though I don't know enough about EEG readings to predict what they would be.

In general I worry that this is not a helpful line of thinking to pursue. Finding these effects would show that the time I've invested in meditating has affected the functioning of my brain with respect to attention and perception. Would this really be a surprising result to you? I would expect that a person who pursues any exercise in attention and perception is likely to show differences in attention and perception compared to a person who doesn't, simply due to neuroplasticity, even if they aren't exercises in attention and perception that would ever lead to enlightenment. I don't see that being able to demonstrate these differences would have a very large bearing on the claims I've made that people here have found controversial (though it would have some bearing on them).