distributor springs light enough ??

just finished curving my mopar dist.
installed a pertronix III unit and flamethrow coil.
changed out the slotted plate for a 8* .375 with a long looped stock spring and a medium spring.
when I'm setting up the total timing @ 34* and 20* intinal and total at 2500 rpm ,vac adv plugged ... the timing still wants to climb some more before it stops..appears to be another 4* or better.timing still wants to climb at 34* total and is not all in yet.....
is it because the stock tighter spring with the big loop is not stretched out to the max yet and probally needs a lighter spring in there to bring to a faster total at 34* ?
when tested right now.... it is has the stock big loop spring and a medium spring someone has replaced from the real light stock spring .
Thanks fabo's