So, your professional opinion needed. I know you loose some strength on 6061 when you heat it. Do you think I should add gussets out to the sides of the platform?For the angle of the standing platform what I did with mine was set up in the saddle on the ground, find your sweet spot, put the angle finder on either your back or chest, record angle, mathematics, fabrication, prep, weld,and enjoy. 15 was too shallow for me but could be right for you.....
Good job on the preheat.....almost sounds like u know what ur doing