Probably they will have virtually no effect.
There are two quite different things that people call radials, or radial systems.
One kind is (typically) λ/4 radials, usually in free air. These, because they are open-circuited at the free end and 1/4 of a wavelength long, are in principle short circuits at the attached end, and (by shorting them out) prevent RF currents from flowing down the outside of the feedline toward the transmitter. That is, they're an RF choke, or a kind of balun. The RF short circuit reflects energy flowing down the outside, sending it back up to the antenna so it'll do some good. You see them on what are misnamed ground plane antennas. Your radials, at five feet, would work this way, perhaps, at about 49 MHz (or odd harmonics of 49 MHz) but nowhere else.
The other kind of radials are long wires (typically several wavelengths long) placed on the surface of the ground, or slightly below, or a bit above. These provide, essentially, a reflective surface that is less lossy than the local dirt is. Think of them as shielding the dirt from your signal so it'll be reflected toward the horizon (or the ionosphere) instead of being absorbed to heat the dirt and cook the worms. Most verticals will work much better with nice long radials of this kind -- or a good natural reflecting surface such as salt water. If you're on baked clay, you need radials. If you're over salt water, you don't. But five feet won't help much.
My old friend Whit Griffith, N5SU (SK), designed and built Voice of America and Radio Free Europe HF broadcast stations for a living and was a true expert. He once experimented by building an HF vertical and gradually adding radials, measuring the efficiency after adding each radial (they were many λ long). He calculated the radiation resistance (since he knew the vertical's length and his transmitting frequency), and measured the antenna's impedance at the feedpoint. If the measured impedance (or the resistive part of it) was, say, twice the radiation resistance, then the efficiency would be 50% since the power delivered to the radiation resistance would be equal to the power dissipated by the ground-system resistance that was in series.
Anyway, he'd add radials, measure the efficiency, and repeat. He found that eight or so radials were not too bad, but could be improved quite a bit, but there wasn't much point in putting down more than, say, 120 radials.
It was also clear that radials shorter than several wavelengths were a pure waste of copper.
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-- Carl
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