What ring height do people use on their Ruger RPR  ?  I tried to use .92 Seekins rings; same as on an R700 build and I couldn't get my head down low enough to see through the optic (Vortex Viper PST2 5-25x).  I then got .97 Seekins rings...which didn't improve the situation.  Again, what height rings are recommended ?

This is why those cheap $10 rings at Wal-Mart exist.

There's been a time or two I've had this problem so l try the sizes Wal-Mart has on hand.

I'll clamp them on the gun and pull it up to my shoulder - minus the scope,  to check the height.  If it looks close then I'll lightly mount the scope.

Sometimes the cheap rings get thrown into the spare parts box, they work okay for .22s, but something like the see through rings l return.  I'll never use them for anything. So treat the packaging and products gently.  And keep your receipt.

Once you've established the height order what you really need.

Most are using AR height (1.5") rings or mounts.

1.5" height would be my recommendation.  The RPR with it's straight-back stock is more like an AR10 than a standard hunting rifle in regards to height of the comb on the stock.  
It will be hard to get a good cheek weld with anything much lower than that.

IMO, you'd be better served dumping the rings and getting a good 1-piece scope mount.  Saves you a lot of hassle ensuring rings are properly aligned and all that.  
Burris P.E.P.R or Aero Precision if you're on a budget.  LaRue LT-104 or ADM mount if you're looking for higher quality.  SPUHR if you're going balls out.

If you're dead-set on scope rings, look at Badger Ordnance.  http://www.badgerordnance.com/scope-rings.html

I used 1.45" height Vortex rings which are just Seekins rings rebranded.