I'd be creative on the body fixtures. Concentrate on what 1) you actually need to support your picking/strumming arm and 2) what you need to support the guitar on your lap when sitting down. It doesn't have to look like a guitar outline. You only need a small portion of both the top and bottom curves to achieve this, so on top you could have a T-shaped attachment with the top of the T curved downwards, and an inverted T on the bottom also with the top of the T curved downwards to rest on your leg.