I've spoken with my good friend Bob W3BBO about this in the past, and he put the bug in my ear about using coaxial stub filters, instead. He has some experience using them and he told me they worked well for him.
I did some Googling and searching of the ARRL Web site last night and found this:
http://www.k1ttt.net/technote/k2trstub.html as well as this YouTube video:
As I'm going to be replacing the coax out to the Butternut as soon as the weather cooperates, I'll have a useful purpose for the old coax, instead of just tossing it. It would end up being a lot cheaper than purchasing toroids and capacitors and enclosures and antenna sockets needed for the K4VX filters. All I need for the stub filters would be some PL259s (which I have) and a few T-connectors which I can get at a local hamfest.
If they don't work as well as I'm hoping, then maybe a combination of the K4VX filters along with the stubs can be used next year. But it's already mid-April and time is growing short. Field Day will be here before you know it. And even just the stub filters will be better than the nothing we've been using.
72 de Larry W2LJ
QRP - When you care to send the very least!