Andrew mate, screw the rest of them, put those plates under the others and do it right.
Take it from me, I recently pinched a nerve cluster in my spine and I'm out of commission for easily a month, if everything goes 100% well in the healing and rehab.
If it's hurting your back or feeling uncomfortable, fix it.
You can also try and use two of those aerobic steps and put the stuff on that.
When the bar is so far down, your lumbar spine area automatically curve, that's when injuries happen.
It happened to me with just a 25kg plates putting it down, and I can't even get out of bed in the morning without help it's that painful.
Don't take chances, I was lucky I didn't get a stress fracture or slip a disk.