The advice and recommendations in Adam Heard's videos on elevator design were absolutely critical to our team being able to design and build a robust elevator this year:
https://m.youtube.com/channel/UCX0Y091TMRKi8PqNfYoImiw
My only additional comment to those would be that if you do not have precision machining capabilities then makes sure to get as close tolerances as you can when building the elevator. We went with mostly COTS parts but our aluminum tubing of slightly differing lengths pushed the frame slightly out of square.