There’s no need to fret over exact lengths for a ground-mounted quarter-wave vertical’s radials, as they will be de-tuned by the soil. How much? It depends on the location, moisture, etc. So, again, don’t fret over it. More short wires are better than fewer long wires at HF.
All this is why poultry “netting” (fencing) works well spread out around a vertical, as does Faraday cloth. Neither is tuned at all, because there are too many variables.