I'm working on getting quotes from local electricians on installing a 14-50 outlet. I'm working off a pretty full panel. Fortunately, there's already a 5-20 outlet in the garage on a dedicated breaker that my landlord has authorized me to repurpose for the 14-50. I've included a photo of my panel. The circuit that can be repurposed is the top of slot 10, labeled "Vaccum". My understanding it that two of the circuits (7 and 9) could reasonably be replaced with a tandem pair, leaving room for a 50A breaker on what's currently the vacuum circuit (though this may require upgrading the master breaker, at 100A now). However, at least one of the electricians is saying that the panel is full and would have to be replaced, which is a much more expensive job than just reorganizing the current panel. I'm pretty familiar with electrical work and house wiring, but not with the internal workings of a breaker panel. Am I misunderstanding how tandem breakers can be used/swapped in, or should this be possible without requiring an entire panel replacement?