This is according to Lennox dealers website for approved matchups and this is with a piston. I would just keep a eye on the downstairs humidity but unless it is oversized it should work better especially with the variable speed. Don't let the people here make you thank you made a poor decision. From where we are we do not no the exact situation. There is a good chance everything was done properly. They should be able to supply you with a copy of load calc if you request it. Like we preach on this site all the time if you feel comfortable with the contractor and they are well qualified you should be ok. There just seems to be a lot of Carrier and Trane fans on this site and alot of Lennox haters. All brands typically work well if installed properly.