Aikido is not just a series of techniques for countering specific situations. It a systematic method for developing aiki, the ability to harmonize with the strength and will of another.

With that in mind, questions such as "what if an aikido guy goes up against a boxer" becomes irrelevent. (As a side note, you are one of about a gazllion people who have asked this question, many of them with their fists, and an aikidoka worth his belt will be able to answer).

When I came to Shin Budo Kai to think about studying aikido, I had the same exact questions in mind. So, I picked out who I thought were the hard cases and went at it. I threw punches, went for takedowns and choke....all the good stuff. Fortunately, they were not offended and were glad to answer me with throws, locks, strikes, etc.

Also, it is very important to resist techniques from your partner in a constructive way. You need to slowly build your ability to avoid having your technique stopped through recalcitrant resistance (using muscles to stiffen your joints). Also, many aikido techinques are built around the idea that the person will resist. It is that resistance or attempt to recover that leads to successful execution of the final technique. Eventually, resistance and attack becomes a gift.

I would not be studying aikido if I hadn't used my san shou experience to test it out.