SilentMantis,
It is good that you practice with other stylists like boxers.
There are a lot of good things to be said about boxing.

I believe that under boxing rules the method is close to perfect.
In other words you have to learn that style to play that game.

Since those 4 punches are already in Mantis it couldn't hurt to do that.

If you have a friend or partner who is willing to try his boxing vs your Mantis that is good too.
You will have a partner who is trying to hit your head very hard while you try to apply your Mantis.

This is a good way to practice after you are very fluent with some of your 2 man drills.

As for strategy.
My guess is your opponent is thinking offensive, not defensive.
You should have this mindset too.

NorthernMantis,

I don't suggest the pushkick because that is more useful in competitions where it is against the rules to grab the leg.

Youngmantis,
Although the knee kick seems good in theory rarely does it do anything(not including the takedown version).
This is from my own experience in local skill testing matches.
All I get is scraped or cut skin, but doesn't stop me.

This experience matches my shrfu's experience.
When the knee is bent it is very strong.

Also, this strategy, as well as the push kick strategy is "keep him away" mentality.
Contrast that with the "KO" stratagy of boxing.

More?
Mantis has an interesting habit of using the left hand to "seal" the opponents right hand while simultaneusly using the right hand to perform straight punch-hook punch combo.

This is called Di Lo(under leak) and is found in many Mantis forms.