If you are saying that your will do an oxalate challenge, as the first one after hitting baselines, I think the plan you have will work so long as your baseline includes low oxalate. Oxalates may take a while to get out of system though, I really don't know. If you are not eating low oxalate at the moment but low everything else, personally, I would just eat the low chemical diet and see if you get to a baseline with the oxalate in. There must be a good reason that the RPAH diet doesn't consider oxalates as part of the foods to be avoided. If you really can't get to a baseline in 2 more weeks then cut the oxalates down to lows and see what happens.