Highest recommendation to using one of the Schwalbe Marathon Plus tires for sale (OEM site, Amazon or such as via Peter White who also makes great wheels for tandems). These tires tend to be taller profile tires vice fatter per say which may help with your frame. The last a very long time and ride smooth. Even after many years of heavy loaded touring on tandem, have never had a flat with any of them. If you are looking for gram-savings, then these are for you as they are not lightweight. Hope that helps. /k
https://www.schwalbetires.com/bike_t...s/marathon_420
https://www.amazon.com/s?k=marathon+...b_sb_ss_i_1_18