Lapper battens

My L28 came with four lappers, all but one in good condition.  All are North Sails.  They are all very similar but not identical. For example, one has three partial battens while another has four battens: three partial and one full length.

The lapper with three battens however is missing the actual battens (they are obviously removable).  Two of them are 24" long and the other (the uppermost) is about 18" long.  The slots appear to be a best fit for a 3/4" wide batten (which is interesting because my other lapper has 1/2" battens in it).

I'd like to order replacement battens so I have two fully functional lappers.

My question is: any particular type of batten I should get?  tapered or non-tapered is specifically what I'm thinking.  West Marine sells battens in fixed lengths as well as batten stock you cut to size yourself.  Fixed length available as tapered or non-tapered.  DIY lengths are non-tapered stock only.

Thanks for the help.