We've sometimes seen as much as 40% more power by tilting our panels toward the sun, but several things affect that, like - which way our RV is facing, the cleanliness of our panels, the degree of cloud cover, how far north or south we are (especially during winter months.) All those things affect how much power we're going to actually see. https://youtu.be/PUEBOQ5U52o
Before we designed an automated system, our panels were flat-mounted with standard "Z" brackets. They held our 160 watt panels down just fine, but I always knew we weren't getting as much power out of them as we could be getting. There are a variety of manual tilt kits out there, and other than being a PITA to use, I haven't heard anyone complain about how well they work. You just have to climb on and off your roof to adjust them.
If you've got the room, another viable method of getting more solar power is to simply install more panels. The percent of increase in power will often rival that of tilting your existing panels. Then you wouldn't need to tilt them at all.
Kev