I am the seventh master that plays with the arms crossed, and this cover is better in armour than unarmoured. What I can do with this cover are the plays before me, namely the middle bind which is the third play of the first remedy master of dagger. Also I can turn you by pushing your right elbow with my left hand. And I can strike you in the head or the shoulders immediately. And this cover is better to bind than to do anything else, and is a very strong cover against the dagger.
The 7th master makes the cover of a high posta mezza porta di ferro dopia incrosada. This is a very strong cover, although the mechanics of the posta limit its reach. You are going to be very close to your opponent.
Due to the very short distance, such close range fighting moves extremely fast. Many people find it overwhelming. Although it comes with many dangers, if you are practiced at fighting in extreme close range, you can quickly gain and exploit any number of opportunities and advantages.
Having jammed the attack, keep pushing forward into your opponent. Let go of the dagger with the left hand. You are perfectly placed to grab your opponents wrist. This transitions you to the cover of the 1st master of dagger. From there, you can progress to any of the plays of the 1st masters scholars. The close range means you can easily bind your opponent. In particular, Fiore recommends the middle bind as shown by the 1st scholar of the 1st master. You can also use the high bind as shown by the 5th scholar of the 1st master.
Alternatively, you can slide your left hand down to your opponents right elbow and push through them. This will turn them, exposing their back and right side.
Your right hand is chambered to deliver a strike. With your right elbow pointing at your opponents face, you can pivot your forearm across the full range of fendente attacks. This gives you the ability to instantly strike through any gap which appears from the height of your opponents right elbow, all the way across the top of their body to their left elbow. Move quickly and take advantage of this.