I've done that very thing at least a few times. Back in the "old" days, we pulled FP for Soarin that did not kick in until 11:20 or 11:30 more than once. You need to get in line the minute that your window opens. With FP+, the Mickey head will scan green 5 minutes before your time, so I would go right then. Soarin typically takes 20 or 30 minutes when you go through the FP line. The pre-flight and ride take up about 10 minutes, but by the time you wait a cycle or 2 in the fast pass line, which you likely will, that will add the rest of the time. Akershus is a lengthy walk from Soarin. You might have to sprint just a little depending on how long Soarin takes you, but you should make it. Sometimes Akershus does have a long check in line, but it should be fine.