hot head off of 9kg bottle - regulator? flashback arrestor? both? neither?

The subject just about says it all.

My partner is using a hot head torch with the tiny bottles, which is not very cost effecient.

She is moving to LPG in a 9kg bottle, and has a hose, but it doesn't have a regulator nor arrestor.

Reading it seems you probably shouldn't use a regulator, but without a regulator the pressure will be well above what an arrestor supports. Does that mean it should be okay not to have either?