Songs written in DAA tuning

I purchased a book that has songs in DAA tuning. I never thought that it may be a problem trying to tune either of my dulcimers to this tuning, however it is. One dulcimer has a 26 1/4 vsl and the other 24 1/2.Either it just isn't possible or the string breaks - even if I tune slowly. Does anyone have any suggestions as to what I can do in order to play these songs? Do Iliterally need a longer vslin order to play these tunes? Can I transpose the songs to DAD or DAGand if sohow do I do so. Thanks in advance for ANY suggestions.