Maybe don't lower it quite so much but I think it'll be better with the sides lowered some. Remember, baby won't sleep in it forever. By the time they are old enough to move around and pull themselves up where there's a danger of them going over the side, they'll have been moved into a crib. By that time, even at the original depth, it won't keep baby in if they want out.
You've probably seen the cradle I built for my son.
As you can see it is quite shallow but it was never a problem. He quit sleeping in it before he could have gotten himself into bad spot. Then it became an ark for the stuffed critters. I was worried that he'd roll over and get the gunn'l down so he couldn't roll the other direction. A number of folks told me he'd capsize it when he rolled to one side. As it turned out, the way it hangs, it's impossible to capsize it.