Replacement windows - flashing question
Okay, so I'm having some very large windows (103"x60") replaced. The windows are currently vinyl and I have vinyl siding with j-channel butting up to the current windows. For replacement, all of the wood trim inside the house around the vinyl window was removed. Upon replacement, my contractor simply cutout the old window and installed a new window in the rough opening. On the original window, there was never any flashing present, no flex wrap around the rough opening, the original nail fin was not even taped, but I never had water problems, just horrible windows. The new windows that he installed do not have a nailing fin, instead the window has an accessory grove that he snapped a cover into that extends outward and covers the existing J-channel. He used silicone to adhere the j-channel to this new cover. He also caulked the window to the j-channel in hope that it will keep water out. Needless to say I'm a bit concerned that I will have a water problem and want to stop him before he does more windows. Are my concerns warranted?
Also, on two windows he measured the old window incorrectly and as a result the new windows are about 3/4" too tall. They fit in the opening but are very tight top and bottom in the opening, no way to even insulate, perhaps caulk but that's it. Do I need to fear expansion come summer and troubles with the windows?