I'm not sure what boost level the 1G DSMs ran, but if you are going to keep it conservative, see if you can get a wastegate actuator from a Conquest or Starion, 88-89. They were a dual port(actually 3 port, but 2 ports were tied together) actuator, 1 port set to open at 7.5psi the other port set to ~10.5psi. Go to
www.starquestclub.com for a good classifieds section.
As to the issue of boost creep, I was running 16psi on my Conquest(2.6l SOHC), and never saw any issues from the TD05-12a. However, there are larger wastegate flappers generally available on ebay, which would probably be a good mod to help controller boost spike and get a tighter hold on lower boost levels. I know my 12a could still hit 8psi with the wastegate wide open(flapper broke, and fell out of wastegate).