One thing I noticed in doing this, as per John's guidance pertaining to the top hats, the hat won't sit flush if you line it up with the end of the spring. In factory garb, the Ion strut assembly comes with the tab pointed at the 12 o'clock position. This is the alignement I have always used for the hats when doing any lowering springs on an Ion (Progress, B+G, Eibach). To do Canuck springs (or seemingly any), you have to have the tab pointed at the 9 o'clock postion to have it match up with the end of the spring when the spring is sitting properly aligned in the bottom of the mount. Later in his write up, he says something to the effect of the tab ending up in the 11 o'clock position, which is nowhere near the end of the spring.
Having all three different springs side by side the other day (Canuck, Stock IRL, Stock SS/SC), they all have the exact same start and stop points to the winding of the spring. If you mate the tab up to the end of the spring, you end up with one tab pointing straight forward and the other straight backward when mounted to the car. I was perplexed by John saying this in his write up on GMSC, so I tested the theory. I am not challenging John in any way, but I took the used stock SS/SC springs first and rotated the new hats (with shims) on my IRL struts so that the hats matched the ends of the springs then assembled everything and drove. The car pulled like crazy to the left. I thought maybe it needed aligned.
But before I did that I wanted to make sure this was the case. So I took everything back apart and realigned both hats to the 12 o'clock position with the stock SS/SC springs. The car rode like the stock IRL springs. No pull, wheel centered, perfect. My car was perfectly aligned (steering wheel and all) before doing any of this and it went right back to that feeling with the SS/SC springs and hats. So now back to the Canuck springs that I was originally trying to put on.
(Long story short, Canuck sent me Cobalt springs instead of Ion springs so instead of waiting for the return/exchange game I just decided to do the Cobalt hats since I found some locally and cut my own shims using trial and error and then just used rubber tubing around the top coil as in isolater. They have agreed to a partial refund for my troubles.)
When I did the Canuck springs, I also did a set of rack spacers intended to move the rack back to alignment for a 1.25" drop. I assembled everything and put the hats to the 12 o'clock position like stock. Now the car rides perfectly straight, no pulling or anything, but the steering wheel is slightly off center. I can live with that until I get an alignment, which will hopefully cure that. It seems the rack may have shifted to one side or the other possibly and I'm thinking pulling one rod end in and one out will realign the wheel. So based on my experience, the question is...
Do the tabs in fact go to the 12 o'clock position or to the ends of the springs?
I always used to line it up at 11 o clock, but the workshop manual says tab to end of spring. So who is to argue? The Ion top mount rotates on that spring hat anyway so it makes no difference where the spring hat is compared to the top mount, only where it is compared to the spring, and the top mount is keyed to the strut hole with a pin.
The alignment issue you have is nothing to do with the struts and all with the fact that if you disconnect the rack bolts to do whatever (spacers, clean the cradle) the chances are you will have to re center the steering wheel by moving tie rods. The steering wheel is keyed to the column with a master spline so the old trick of moving the wheel wont work.
If you dont use very hard steel for the spacer the metal will not survive, but you will find that out. etc. good luck