The Notta Dilemma - Does Size Matter?:
Here are some stats I stumbled upon at
http://www.rugby-sidestep-central.com/player-sizes-12.html:
The data set I have summarised below is that of the 2013 B&I Lions team, and the Wallabies and NZ Rugby Teams from 2013 TRC games.
Prop: Height (cm) min: 180, avg: 186, max: 193 - - Weight (kg) min: 109, avg: 118, max: 130
Hooker: Height (cm) min: 176, avg: 183, max: 187 - - Weight (kg) min: 102, avg: 108, max: 114
Lock: Height (cm) min: 196, avg: 200, max: 205 - - Weight (kg) min: 104, avg: 115, max: 120
6 - BSF: Height (cm) min: 190, avg: 194, max: 198 - - Weight (kg) min: 101, avg: 107, max: 110
7 - OSF: Height (cm) min: 182, avg: 187, max: 191 - - Weight (kg) min: 96, avg: 102, max: 107
No 8: Height (cm) min: 188, avg: 190, max: 193 - - Weight (kg) min: 107, avg: 109, max: 109
1/2 Back: Height (cm) min: 171, avg: 181, max: 19 - - Weight (kg) min: 76, avg: 88, max: 103
Flyhalf: Height (cm) min: 178, avg: 183, max: 188 - - Weight (kg) min: 84, avg: 91, max: 96
Wing: Height (cm) min: 170, avg: 187, max: 198 - - Weight (kg) min: 81, avg: 96, max: 106
Centre: Height (cm) min: 175, avg: 185, max: 196 - - Weight (kg) min: 85, avg: 99, max: 110
Fullback: Height (cm) min: 178, avg: 184, max: 18 - - Weight (kg) min: 83, avg: 91, max: 95
It is not a huge set of data but in terms of 6 and 7, the tallest #7 was only 1 cm taller than the shortest #6. The fattest #7 was the average weight for a #6.
In terms of a #6 that is a backup lock, the tallest #6 was only 2cm taller than the shortest lock. The average #6 is 8kg less than the average weight for a lock.