repeat

_{Post edited by SolarRide: repeat}

complete level 3 of a mode and a particular shot is doubled.Klingon level 3 causes left ramp to be doubled.
Save the enterprise 3 and right ramp is doubled. Nero 3 and left orbit is doubled, Space jump 3 and right orbit is doubled. On v1.5, the doublers stay for the whole game. Warp 9.1 and 9.9 create double scoring for all features not just loops,saucer and ramps, but only for 40 seconds and these can combine for 4x scoring with L3 or combo doublers. combo shots create hurry-up doublers on a ramp,orbit or the saucer, but they don't combine with L3 doublers.

For PD3 it is helpful to have played KM and EA first for larger scoring, plus getting the ramps and orbits doubled by completing their L3s. Like all level 3 modes if you don't complete a level 3 mode in the allotted time, all shots must be hit again on the restart of the L3, so you are turning the tables on the programmers by intentionally not ever completing PD3 so that you have this big scoring shots relit on the next PD3 restart. Also PD3 holds the values from PD3 restart to restart if on the same ball, so that it just keeps getting bigger and bigger. 16M point shots are not uncommon by the time you get to the 3rd or 4rth retart on the same ball, but just try to hit the multi-colored arrow shots which are worth more. it will be interesting to see how PD3 builds on the restarts without playing KM and EA and also without getting the L3 doublers. It probably builds but just more slowly than if you do the above.

BTW SJ3 is a nice runner-up to PD3 in the event that you accidentally finish PD3 and can't restart it.

Well first let's distinguish between doublers and multi-colored shots: combo doublers are totally independent of mode. If you shoot the left ramp, for example, the right ramp and right orbit will have a hurry-up doubler lit. It doesn't matter what mode you're in or even if you're in a mode.
Now I think the SJ3 multi-colored flashing shots, which are twice the value of the uni-colored flashing shots start out on the right orbit, rather than the left ramp like PD3. As KME suggests, PD3 would be your first choice. But if PD3 unavailable, maybe you had to do a slap-save and hit the saucer which was the last shot for an accidental completion of PD3 or you find you're on last ball with SJ1 and SJ2 completed but no progress yet on PD, you might keep restarting SJ3 rather than trying to go from scratch up to PD3. It's just an outlet for an odd-ball situation.