Young men 'checked out on Spitfires' would previously have flown Tiger Moths (or Stearmans etc. in the USA) as well as probably the Miles Master or Harvard. Plus there was a war on.
I recommend that your syndicate must all be competent to fly tailwheel aircraft (see CAP804 for tailwheel differences training guidance) before you attempt to sign them off to fly the single seater.
Even if something isn't legally required, you must still exercise a reasonable duty of care. Plus the rest of the syndicate won't be best pleased if someone groundloops and destroys the aircraft because he/she hasn't had any dual time in a tailwheel aircraft.