hi bruce,all three of my 126's had some kind of glue in place to hold the mouldings,but i have replaced only (original) the aircooled ones and have not used glue.they hold very well,
as mine were pr used,they were already formed to shape,i guess you will have to gently heat them to fit,i would not bother with any ''gunk'' to fit them,its good to remove them time to time and wax the inner gutters.