I have done the 2 strike ball/1 plastic ball arsenal for numerous seasons now and it works fairly well.  However, when I look at my arsenal though, I have it set up different than what your intentions are.

Currently my THS arsenal is a Zero Gravity, Frantic, and Plastic.  Usually I start with the Frantic, the weaker of the 2.  If I need to move considerably deeper into the lane (and into heavier oil) after starting with the Frantic (anything more than 5 boards which is rare), I will go to the Zero Gravity so that it will make the turn.  It sounds counter-intuitive but it works well.  Also, if I need more hook to start the night, which does not happen often, I will go with the Zero Gravity. 

You want to do the opposite, which is to start with the stronger of the 2 and finish with the weaker 1.  This is do-able too and is just a different mindset. 

On a THS, with a 2 ball arsenal I would not go to extremes.  I would go with equipment that will cover medium-heavy (Zero Gravity) and medium-light (Frantic).  I would not go with a low rg oiler and pair it with a high rg weak pearl - too much difference between the two.  What balls are you thinking of using?

last year even though i carried five with me i routinely went with 2 balls every week. my fresh ball was an IQ tour solid. and my transition ball was a cobalt vibe. i generally throw mostly symetric cores. i dont think you need anything crazy on house shots. there are so many choices that on a pattern like house shots pick one ball thats lower RG medium/high diff. with some surface and one thats a little higher RG and medium/lower diff. with less surface. every company has their version of those. your proshop should have a better idea for your specific house since you guys know how your house shot plays.

I would go with a Motiv Primal Rage or Storm Optimus for medium to heavy. I would go with a Motiv Tribal Fire or Tribal for medium to light. I'm a lefty with slower speed and lower revs and use the Rage and Tribal on most shots. I do have other balls, but these two fit a wide range of conditions. Saw the Optimus in person and it would fit the medium to heavy conditions very well also.

Thanks everyone, I have been looking at a ZG, since lower rg balls can sometimes run out of punch for my lower rev, lower speed style. 

Does anyone think a Zero Gravity could be a good step down from my lower rg, dull, early roll layout, Track 811 C/T?

Otherwise, pick a good pair of Storm balls to use on an oily, left side, THS.

Extra info:  Speed ~ 15 MPH at release, Revs ~ 240-250 rpm, Rotation ~ 65*, Tilt ~ 18*.

IQ Fusion, and Hyroad?  Looking to keep the gap between balls reasonably close.

IQ Tour Solid and HyRoad are great compliments without breaking the bank. Depending on how the pattern plays, front to back, you could go Hysteria and OutCry/WipeOut. I would recommend one shiny and one dull piece since you are mainly rolling on ths. And with what Storm/Roto currently have available, you can compliment in many different ways depending on what you are looking for reaction wise.

Angular dull: Sinister, Zero Gravity, IQ Tour Solid(can be smooth with layout), HyRoad Solid, Disturbed
Smoother Dull: Hyper Cell, Asylum, Marvel S, Rumble, WipeOut, OutCry
Angular Shiny: Byte, IQ Tour Pearl, Deranged, HyRoad Pearl, UpRoar, Punch Out
Smoother Shiny: Totally Defiant, Hysteria, Optimus (can be Angular), Marvel Pearl, IQ Tour Fusion, HyRoad, Lights Out

thus is how I see most of the line up. Some will agree and some will disagree. Different releases and Rev rates/ball speed will move some balls around on the list. For me the Sinister isn't as angular but does change direction quicker than most dull asymms. The IQ Tour Solid for instance can fit angular or smooth depending on layout and surface. It is a great dull benchmark that I would recommend for every style. I hope some of this helps!