A few weeks ago I pretensioned the spring cord in one field frame to 350hz. This should give about 20% increase in power with the same amount of washer rotation. While the field frame bars are slightly more bent now, I don't think the bend is excessive. Thus it seems that I don't have to make new field frames to reach "full" power, which obviously saves me a lot of time and effort.
Before restringing the other field frame I'll do practical to compare how much more resistance the 350hz frame offers compared to the 320hz. I have some old otherwise useless limbs which I can use for this testing. Hopefully I have some results of this tomorrow.