SIze isn't everything. Just ask Dogs fans.
How effective our forwards are will come down to McInnes and McGregor.
Matt Elliot did a brilliant episode of The Breakdown where he compared the usual sets of 6 from top clubs (Melbourne and Canberra) and bottoms clubs (we were the example). In the good situations, on every play the hooker had 2-3 options for ball receivers, including one of either side of the ruck, and all timing their run perfectly. This gave the hooker time to move without being swamped by markers, and put the defensive line in 2 minds from the get go. The hooker would pick the mark, and as that forward hit it up he still had an option of tipping the ball on, which held the defensive line up. It's a very minor, basic thing but once you look for it, you notice all the best teams hitting up like this. It relies on a solid hooker and forwards knowing their jobs (i.e. A game plan).
Then he showed our attack. Before the ball was played, you could tell what was going to happen (whether it was a winger scooting or a 1-out forward). There was no additional option. Couple that with the fact that the forward hitting it up had to amend his run to catch Rein's pass, and the defense would clobber them. It wasnt until tackle 3 or 4 that someone was able to get any decent sort of play-the-ball, and it would be a result of them winning the initial contact.
Unless things like this have been addressed, the biggest pack in the world wont help us.