I was able to do the same. Only I left the arm on the seat. Wiggled it up down while pushing/turning adjuster. 
The other arm I tried to fix for a buddy. The adjuster would not thread back in. Had to pull the cover off and fix. Luckily he does not  care about how anything looks. The cover tore on the side facing seat. 
Alistair repair blog is fantastic.  Gravel driveway mechanic king!

Bill M
Westerly,RI