I am confident that you already have explored the options in

Document Options - Clefs

If those options are not enough, here are some other ideas:

1) Try increasing the size of the {clef change} clef. The default size is 75 %.

2) Try another clef font.

I couldn't find any specific commands in the Document-Clefs options for mid-measure clefs but did find a solution in the Document-Music Spacing options. By putting in a larger value in the Minimum Space Between Items section (15 EPV's for example) this automatically increased the (previously too small) space after the mid-measure clef.

Two year old thread, my friend. I doubt the OP is still interested.

Incorrect, I'm always interested in Finale hacks.

A rare person indeed that still monitors a two year old thread.

A much more plausible answer is that I receive an email when the thread is updated.

The fact is, if it  helps that is a good thing. I had no idea the forum kept tracking that long so we both learned something today.

But these questions and problems only go out of date if the issue is resolved by Finale and unfortunately, this only seems to happen very slowly, if at all. I do feel that the Finale software engineers could look more closely at the forums to see what problems people are having and which of these problems could be resolved by easy tweaks to the program.

My impression is that there was a passion for perfection at the beginning but now, for whatever reasons, the structure is unresponsive, certainly to the forum feedback but also to the suggestions for improvement.

I have no doubt that MM monitors this forum. Why they don't do certain things, your guess s as good as mine. I do think a lot has to do with causing more problems or breaking something else unforeseen.  A small seemingly harmless tweak can have very undesirable consequences not to say the clef placement would.