I went through the PE statistics database quite a bit when I started out, probably as much as anybody has. Here’s my take on the often asked question of realistic PE goals.
1-4 cubic inches: An easy goal. If PE “works” for you at all, it is doable with moderate dedication. 98% of guys can achieve this (roughly the % that PE “works” for), if they truly want to.
4-8 cubic inches: A reasonable goal for most guys, provided high dedication over a few to several years. However, some guys can’t get there no matter how hard they try. I’d estimate 80% of guys can achieve this, if they truly want to. In the database, only about 35% of guys get there, because this level begins to require a significant time and effort commitment.
8-12 cubic inches: A difficult goal, borderline unrealistic for most, requiring high dedication over several years to even have a chance at it. Some lucky easy gainers will get there faster and with moderate efforts. However, for the vast majority of guys, a gain on this order will require that PE become part of their lifestyle, a regular practice for several years. I’d estimate 20% of guys can achieve this if they truly want to. This is a gain level where some guys (those with big starting sizes) would not even want to gain this much because it will begin to put them in the “too big” category for some women. In the database, only 8% of guys get there.
12+ cubic inches: A colossal goal, unrealistic for most, requiring complete dedication over many years to even have a chance at it. Most guys who get there are “easy gainers” who also put in all the time, learning, and effort to get there. You have to truly want it, and be a little lucky, to achieve this goal. Note that very few guys actually want to gain this much. Many say they want this much, but guys with average or big starting sizes will get to “huge” or even “monster” status before reaching this gains level and stop at the previous level, completely satisfied in their ending size. I’d estimate 5-10% of guys can get here IF THEY TRULY WANT TO. Again, very few guys truly want to gain this much, and the time commitment required starts to become highly prohibitive in the later years. PE must be a lifestyle practice to achieve this goal. In the database, only about 2.5% of guys get there.
Your goal of 7.0” x 5.5” would be a 7 cubic inch gain from your starting size.