Two Royal Navy colleagues with whom I played ( Ned Starkey from Liverpool and Don MacKenzie from Glasgow),both managed to play bowlbacks by sort of cuddling the things tightly to their bodies,and hanging on for dear life ! That was in the 'sixties,when flatbacks were much less common ; in those days,even The Dubliners,or at least John Sheahan & Barney McKenna ( as on The Leaving Of Liverpool instrumental break) were using them.
             I won one (a Brunswick) in the raffle at Banbury last year,but haven't got it set up yet !!