@ Conservative Man - You probably don't want to start right out at 8, or even 6 or 7. Of all the positions on the field they're the most demanding physically and mentally. Not only do you have to play with the forwards and do everything associated with being a forward, (i.e. rucks, mauls, scrums, line-outs, tackling giant pacific islanders intent on breaking your skull, etc.) you have to support the backs too. This means while you don't necessarily have to be fast, you do A LOT of running. From personal experience playing at the high school level, more running than anyone else on the field. Also, while you don't necessrily have to be huge to play 6 & 7, (8's are usually pretty big) you need to be able to hang blow for blow with the biggest guys on the pitch. Loose forwards get the best (or worst, depending on perspective) of both worlds, so I would suggest you start out at something more along the lines of wing. And no forwards can really afford to be thin.