Be careful with including experimental stuff. It is experimental, they are not kidding. The smaller the kernel the better, but make sure you don't accidentally throw out something you need at boot time. The available online help will give you tips on what to do. If you're not sure, don't change it.
Interdependencies are sometimes delicate and hard to grasp.
Better a kernel that is some kilobyte larger than strictly necessary than one that doesn't work at all. Next save your new configuration. Compile time depends on system and kernel configuration, of course. These 'files' are actually links. Leave them in place and trust M's init script to sort things out, i.e. to change these symlinks according to the kernel you are booting.