he is big now and from what I have seen is improving fast. I belive Radford knows better then we do

You think radford doesn't know masi will be a better prop in 4 or 5 years than he is now?

This is great news. I feel Matongo has a huge future in the game. As has been stated, still only 21 and he has physically developed significantly over the last 12 months.

Obvious move by the club and good that he knows where he stands. He has all the physical attributes for sure and will get stronger still no doubt, it's now about gaining experience and having real belief in himself at the top level and progressing forward and make his next target to be a first XVII player.
Good luck to him

Good news indeed
IMO running style needs to be a bit lower on collision
Add offloading to that and we have a winner