It can work but the biggest problem is current capacity is generally compromised this way. The best way is to simply design the power supply right in the first

It can work but the biggest problem is current capacity is generally compromised this way. The best way is to simply design the power supply right in the first place! Today that's using a buck-boost isolating switcher to create BOTH the +5V and -5V at the same time. Or a linear with the proper center-tapped transformer. Power supply design is NOT something to leave to the last step or to give short shrift. When I worked at Hewlett-Packard, there was a story going around that a division decided to give a summer intern the job of designing a new product's power supply. It did NOT end well - the product suffered field failures, cost a ton in warranty costs and delayed the full release of the product by a year. After that, power supply design was something that the top engineer had to be involved with especially in an intern was involved. This pairing actually resulted in both a better product and in having the intern learn more and be more likely to work for HP full time eventually.