IT all depends on the 049 engine you are using.
If its a Cox 049 read valve engine 35' x .008" lines a would be the limit.
If you are using Cox 049 TD, Brodak 049, or Norvel and AME 049's you can go to 42' lines.
This is what I'd use here in Aus but you'll probably get other opinions from your end.
Fredo