I tried the way you did it...it is weird...and it merged everything...don't want that...BUT

I would do this...

Take full song......Merge it, but start the MERGE on the next BAR at END of song...

Eg,,,64 bar song merge all and insert at bar 65...Now you have 128 bars....I would then take from the last half of the song the 16 bars and INSERT where I needed...and delete the rest of additional bars..

OH, I ALSO DID THE COPY FIRST AND INSERTED THE SILENCE,,,THEN I WENT BACK AND PUT THE BARS IN FROM THE LAST HALF OF SONG...SILENCE WAS FILLED WITH THE TRACK YOU COULD NOW SOLO ON...

Once I reloaded it everything was there...

IT'S CONFUSING AS HECK BUT CAN BE DONE