Kent, the company is in New Jersey I believe and they already have the measurements for the SM. Pretty straightforward to install. It took me two days. We have a 9 foot RIB and a 9.8hp 2~stroke outboard. I will lift both when at anchor but prefer to island hop with the outboard on the rail. I put the dinghy on the aft deck for longer passages.So far, with about 3000 bluewater miles experience with it, we are satisfied. I have added a cross rail for lateral support (does not come with the arch itself). Also, I will be installing a light gauge wire mizzen masthead stay that will split to each top corner of the arch to protect against any shocks.