Yes Peter.
The late Ian Barnes suggested going to 4th LS but the general consensus was up to 3rd LS.
The stats as per Malcolm K (run over 100,s of thousands of races) indicate that horses which ran 5th or worse LS are more likely to LOSE next start.

I would be hesitant also to bet a horse that was a backmarker as against a horse that was a leader or races on the pace in the majority of their races (1.e 4th to 6th on the home turn)

Also horses up in the weights 55KG + win more races than those down in the weights.

Cheers
darky
ps .The top 2 racing form papers are SPORTSMAN and ( WIZARD online )