Can't speak for OS having never used it, but tillering for maximum weight with warbows is pretty much all I do at the moment. I start with dimensions from medieval bows as thats what I make, rough out the stave, check the dimensions again and then essentially finish the bow, rounding the edges, sanding smooth, fitting nocks etc, all before even long string tillering.
Then I start to tiller, and assuming we're talking about full compass, bendy handle bows I tiller the mid-limb and fade area until the tips are moving by about 7" (because when the bow is fully braced the tips move a lot more) then fit a braced string almost at full brace and complete tiller to maximum length (30" for instance) making sure the middle starts to move towards the very end.
Provided the tiller looks good the weight is irrelevant as there's always somebody out there who needs a bow at whatever that weight may be. I much prefer this to making a bow to a specific weight.