I have scissor trusses in my 30x40 shop. I built it this way to accommodate a lift - but have not purchased one yet. The pitch of your roof will determine what your center height will be - I have a 6/12 pitch that gives me nearly 15' at the center. If you offset your lift towards one side or the other - enough room to park your daily driver on the other side - you should still have your 12.5' ceiling height. Rough approximations: If you set your lift 6' from the left side wall, the ceiling height on for the left side of your vehicle being lifted (which is probably 8' from the side wall) will be 12.5'. Assuming your lift is 9' wide - that leaves nearly 15' of daily driver parking space. Plenty of room! FWIW - 30' is plenty wide enough to fit 3 full size vehicles side by side by side. By using my automotive "roller skates" - I could put my lift in and still park 3 wide - but I my shop is 40' long so I have the room to roll my vehicle to the side and then move them forward.