Note that barley malt powder is different from diastatic malt powder. (yupitsvegan.com)
I now have an active sourdough starter and some diastaic malt so was planning on combing both to create a sourdough soft roll but with added diastatic malt, so it has concerned me slightly that you haven't gone this same route and am presuming you think it will be less than ideal. (weekendbakery.com)
Only problem I had was finding diastatic malt powder locally. (wildyeastblog.com)