MV - I did a few expeiments and I think your accuracy may be a bit better than expected and it would be pretty easy to increase it a lot. Check me again on this guys...

I measured two batches of resistors from different suppliers.

1) both differed from the nominal value by about 2%

2) One batch varied by 1/2% plus/minus, the other by about 1% plus/minus. Much better than the stated 5%

3) about 1/3 were very close to the average value.

4) assuming my Fluke meter is accurate to .1 Ohm

So - you could measure 20 or 30 resistors (probably fewer), calculate an average then sort out the ones closest to that for your 2R resistors. Then pair up the ones that are a bit high with the ones that are a bit low for your parallel "R" resistors. 0.1% should be pretty easy to get just by dividing them into high, low and just right. On paper I can get to the .0244% mentioned earlier if I match pairs carefully.

You only need to test enough to get the number of 2R resistors you need. You should be able to pair up the remainder from a pretty small sample. If you do this DONT mix resistors from different batches....