Are you taking the p1ss?
Its all been said before - you're loading the beams wrongly (pulling them in) and those ratchet straps are not at all suitable for load bearing - tying stuff down- sure, but def not load bearing.
Im not sure if you'll snap the straps or collapse the roof first - but either way you'll wreck the car and whoever/whatever is under it.
Buy/borrow some axle stands - if you need it high grab some 6 or 12 ton ones - don't get yourself squashed over $100