You don't scale by changing the paper format. You set the program to whichever paper format you have, then scale the model to a certain dimension you have measured on yourself, then rearrange the pieces and THEN print the whole thing.
Aside from that, 65 lb paper is not heavy enough. You need 200 to 250 g/m², that's around 110 lb and upwards, depending on paper type.
Make sure to read everything you can find about every new step you take. No need to spend more time and money than neccessary.