There has been several Ally tanks on DD bike's,Cobby,Harriet Riddly,Dallas,Ron Jolly,Andy Sheppard, are the ones that come to mind.
Most tanks can be made to fit with a bit of ingenuity, big hammer bit of cut & shut
: ect.
I don't like plastic/F/G or carbon tanks I've seen to many smashed including the one on my DD bike when AK47 crashed it at Pembray.