Hi Dell,  I have had the best experience using Ari Isaac's bass strings.
The sound of his bass strings have no equal.  I have them on my rebuilt
1925 M&H 7-foot RBB and they sound great.  I just now put a set of his
hammers on the piano as well -- the sound is fantastic!  Ari told me
his bass strings are improved even more since I bought mine several
years ago.  I would give him a call and see if he has the round core.
I am sure he could accommodate you.  Visit http://www.isaacpiano.com/ 

All the best,
John Del Carlo