Shnool, the Merit 25 is very similar to the Capri and the J/24. Tuning guides for the Merit say to keep max backstay tension at 1000 lbs or less. I'm using a 24:1 cascade on my boat and it does help. I have the stiffer of the two mast sections (MORC) on my boat.
ctlow - how old are your sails on the 33? looks like it's an old IOR design. You'll need lots of headsails...
Merit 25 # 764 "Audrey"