OK, a bit more on this, from Lester
"The very first Fomula’s were made by Dave Yates, but that was only for a short time before we went to Paul Donohue. We probably had 2 bikes from Dave before getting about 6 from Donohue. It was a struggle getting what we wanted weight wise, the bikes were a mixture of Reynolds road bike tubes, using 753 where we could.
Then in 89 Columbus launched their max tubing which we got. I can’t remember whether there was max chainstay, and seatstays, I think they didn’t but Steve would remember. Anyway Steve sourced some cromoly 4130 and shaped his own seatstays and chainstays which were incredibly light. That’s when the lighter Formula frames started and monostays appear.
The bike in the picture is a Donohue built frame made before Columbus tubing was used."
I hope that clears that up
On dropout almost certainly they'ed of had limited choice at that time, it was a period where the UK frame building industry was almost at its end and investment casting was moving to Taiwan so we'd of used what was available hence the bosses.
I've never seen that seat tube with the embossed logo, it is a piece of history and worthy of restoration.