I like center-grips myself. I have owned a Striker in the past-good accuracy, but the trigger, even after upgrading to a Basix was nowhere close to what you can do with a XP. It was quickly sold.
Are you going to use your current 35 Rem XP to make this build?
Adding weight (heavy barrel), aftermarket stock, and a good muzzle brake
is key to allowing yourself to spot your own shots. Cartridge selection is another thing.
You are wanting to tag a deer out to 500 yards.
With LR cartridges in mind you will lose about 250-300 fps compared to that same cartridge in a rifle length barrel.
Jim See does great work.
In fact, there are several accuracy gunsmiths who do very good work with center-grip XP-100's.
Here are my two latest center-grip XP's:
7mm SAUM (Short Action Ultra Mag) built by Chuck McIntosh Mac's Gunworks
338AX or Allen Xpress (338 Lapua Improved), built by Kirby Allen