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Modern eyepieces are better at reducing the off axis astigmatism of a fast light cone in combination with a more traditional eyepiece. The only coma correcting eyepiece that was available for a short while in the 80's was the Pretoria
I'd recommend a coma corrector like the GSO - only $150 and the problem is sorted ( although the purists may want to add a spacer to perfect the lens to focal plane spacing ) . Coma is linear so using higher mags doesn't help much it still magnifies the coma at the edge of a smaller true field . Some eyepieces do have some ability to correct coma a bit even if its not sold as a feature .
My old 18mm Radian delivered a really sharp edge with an F4 so the Deelite which is a similar design might be worth looking at. The bad images at the edge of low power eyepieces is mainly due to astigmatism - coma is very much less of a component in the mix.
I've been restoring an old GSO 8" F4 , so I 'm going through the same considerations myself but a Coma Corrector will be a definite purchase . I will report back with some evaluation with and without the corrector with a few Televue eyepieces .
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