Picturing it in my head....it does seem if you change the length of the lower it will rotate the housing thus changing the pinion angle. I ordered a set of lowers with the tie-rod style front and adjustable spring height. Should be interesting trying to get that all how I need it.
The ssm direrctions do give how to set the pinion angle, you will need an angle finder, and before you drill the new hole for the new bolt set it up. look at page#5 I sent you.