I can take a barbell out of a rack why not dumbbells?
You have a 6 inch space for your rist, why don't you messure yours.
And the rack is ajustable to go up or down, from declines to inclines.
And it's a piece of cake to rerack or to take them out.
Oh by the way what have you designed? Also i have another one coming out with a pully system
to bring the rack forwards and back.
Untill you try some something i would't knoc it bro, you never know you might like it.