^^ Instead, how about trying WBTB after several hours' sleep (at least 5, in my opinion)?  If you do so, your REM periods should be close enough together that your WILD attempt will likely land you right in REM.  

In other words, because REM periods are far apart at the beginning of the night but move closer as your night's sleep progresses, that 60-90 minute delay should only be a problem in the first couple of hours of sleep; your theory only holds if you attempt WILD at a time when it perhaps shouldn't be attempted.  You might want to change your timing a bit, rather than setting an alarm.