Mentioned here that these Can-Am models are for the road, why would you go off road, or cross country - because you want to. Good on you. I have had my Goldwing on logging roads, don't ask. A Goldwing does not make a good off road bike. Having mentioned this, your options as has been mentioned are limited.
Personally, I would stay as close to the OEM shock length as possible and use the shock spring rate to set the road clearance height. Using the eye-to-eye distance of the shock to set the road clearance height, or assist in setting the road clearance height is not the best practice - JMHO.
The benefit of having a shock assembly that you can change the shock springs for different rates is that you can tailor your suspension to what you want to achieve. Your post is for doing some cross country. You can tailor the suspension, front/rear, for this requirement. When you return home, change the suspension back to what will be your daily riding profile.
If the Ryker shocks have a preload adjustment you can remove the OEM shock spring and install a shock spring with a greater spring rate, I'd start at 250 lb/in. Lots of choice on the web for aftermarket shock springs. It's the shock spring rate with preload that sets the ground clearance. You want the preload adjustment to be no more than 1 cm - seems to be an industry standard. The less preload the better. The OEM shock should give reasonable compression and rebound control.
You can also find aftermarket shocks on the web. These with the proper shock spring set can be used. These may also have a rebound damping adjustment, rebound and/or compression damping adjustments. I've looked at the cost to buy the individual parts to put together a shock assembly and the cost is not much less than going to a shock company such as Elka, M2, and such. When you go down this road, you are your own expert, no other support.
The aftermarket shock manufacturers are not that plentiful, this is a small market. There is Elka, M2, Ikon, Wilber to mention a few.
If you are going to do the front shocks, look at the rear as well. Nothing like bottoming out the rear of your Ryker, or Spyder for that matter. You can approach the rear the same way as the front.
I am going through this same exercise with my 2014 Spyder RT LE. Installed new M2 socks all round. 250 lb/in front spring rate, 700 lb/in rear spring rate (upgrade from 525). The 700 is a bit firm, not uncomfortable, for solo riding, but great for two up riding. Thinking of trialing a 600 lb/in rate rear shock spring. The front spring rate is too soft in my opinion. I have to slow to 10-15 KPH below the posted caution speed on a cloverleaf offramp (caution speed is on the orange speed signs - regular speed on the white speed signs) to go around the curve without hanging out over the side to compensate, and looking like I'm doing a snowmobile motocross. I also want to reduce the preload adjustment from the 2.2 cm to less than 1 cm, need a greater spring rate.
I am trialing different shock spring rates because the shock spring rates from an aftermarket shock manufacturer are a better approximation than that of the OEM and designed to suit a more defined rider profile market, but for my riding profile and the "feel" I get form my Spyder is making me look at some fine tuning. The shocks are way better as well.
Unfortunately BRP information regarding the suspension setup is limited. My Spyder is to have a ground clearance of 110 mm directly under the engine, only spec I can find for suspension setup - nothing on the front road clearance height, not to mention the ACS calibration for adjusting ride height with the air shock.
Hope this helps, and JMHO. Cheers