On Monday, January 27, 2014 8:01:29 PM UTC-6, wrote:

With a 3/8x24 thread mount, I would just use a 1/4 wave.. So much

easier and better looking. Most loading/matching coil schemes are going

to look fairly ugly in a case like that as you usually can't enclose

them in anything.

Pondering.. About the only other easy way to make a 5/8 whip
that would screw into that mount would be to take a glass whip
and then rebuild it into a 5/8 for 2m. You would need to strip
the original wire, or at least partly, then wind a loading coil
at the base, and then pretty much straight up to make the
5/8 element.
That would work.. The reason I call the coil for the 5/8 a
loading coil, rather than matching coil, is the coil is
tuning the 5/8 whip to be a 3/4 wave electrically, which is
resonant. Some ground the coil, and tap at the best match.
But I prefer an ungrounded coil. Why? If it's ungrounded, it
can also be used on other bands. IE: a 1/4 wave whip on a lower
freq.. I used to use my 10m 5/8 ground planes on 30m as 1/4 waves.
But you can't do that with a grounded coil. Works fine ungrounded.