I have normally persuaded the insurers to cover a pilot with limited taildragger experience, albiet with increase excess, so the only catch now is that you must do differences training on a different aircraft. Contrary to popular belief, this doesn't have to be 5 hours, only sufficient to get a sign off from an instructor. Most PFA types I've flown are more flattering/foregiving than the Cub you are likely to train on.
I know someone who picked up a share of a single seater for £200 last year! NO hourly costs, just fuel, monthlies and a share of liabilities. That should be cheep flying...