Ingust,if you want to make things easier for yourself, just use the past ratings provided for free on the tasmanian tab website www.thetote.com.au and go to the form link on the left hand menu and then interactive form. I've found these to be as accurate as any and best of all they are free. To reduce the figures to kilos just divide by 13.3 and round to the nearest half kilo, and then adjust for the current weights and any other bonuses or penalties you feel are necessary.

Why 13.3? I read on the forum somewhere that 20 ratings points was equal to a length on the ratings, so based on 1 length = 1.5 kilos which seems to be the norm with most methods i just divided 20 by 1.5

Might not be everybodys cup of tea, but I find them pretty good, of course it all comes down to which run you wish to choose as your base run. some would use the last run , others best of the last 3 ( which from memory was what Scott used) some may use an average, or the best rating at the distance of the current race. Hope this has been some help and the best of luck with it.