Your instincts are mostly correct, growers gain some ground but don't catch up (neither do they catch up "a lot"). It's amazing how many assume that upon erection "growers" catch up with "showers". Believing that growers catch up falls right in with their belief that black guys aren't any bigger than white guys (since many admit black guys tend to have longer flaccids). They have no choice but to assume growers catch up with showers if they are going to believe white and black guys (and Asians) are the same in penis size.
Research indicates that, generally speaking, growers do not actually catch up. LPSG can't really be used to judge what the standard ranges of growing and shower are. Here is some data from a site many months back. I don't know if more has been added since then.
Also, at Thundersplace, overall the 3" flaccids averaged out to 5.75" erect (grew 2.75") and the 5" flaccids averaged out to 7.25" erect (grew 2.25").
So the two sites' datas match up fairly well.
http://www.erectionphotos.com/softH...dGalleryP01.htm
Flaccid Length--------Averaged Erect Length----------------Amount of increase in inches
1.00-1.49---------------------4.71-------------------------------------+3.50
1.5-1.99----------------------4.89-------------------------------------+3.14
2.00-2.49---------------------4.88-------------------------------------+2.63
2.50-2.99---------------------4.92-------------------------------------+2.17
3.00-3.49---------------------6.07-------------------------------------+2.82
3.50-3.99---------------------6.08-------------------------------------+2.33
4.00-4.49---------------------6.69-------------------------------------+2.44
4.50-4.99---------------------7.00-------------------------------------+2.25
5.00-5.49---------------------7.35-------------------------------------+2.10
5.50-5.99---------------------7.80-------------------------------------+2.05
6.00-6.49---------------------na----------------------------------------na
6.50-6.99---------------------9.00-------------------------------------+2.25
The numbers are somewhat unstable, which more data in each range would likely smooth out. The average increase is 2.5 inches in the chart above. The data above clearly shows that the pc belief that shorter flaccids/growers are just as big as longer flaccids/showers when erect is just not so even though smaller flaccids tend to grow more.