My refrigerator freezer rollers are on steel tracks which support the appliance and raise it up a total of maybe 3 or 4 inches. In my situation, the spacing is not critical as it is for you. The track and roller unit cost about 35 bucks when I bought it in the 2002 time frame.
It is interesting how a person in his 60s approaches a job versus somebody in their 20s or 30s............ I spend a lot more time thinking about things before I do them, especially if there is a lot of weight or other risks involved.....
Smarty