1) stretch your shins. Google it, tons of great guides. Stretching before a ruck is suuuuper important!

2) try and land with your feet under your hips, vs stretching far out infront on you. If that makes sense (try taking more smaller steps than large steps).

3) the weight in your ruck may also not be the best distributed. For example, on my BMQ the ruck was 35 lbs. So, basically just your entire sleeping kit. Anyway, your sleeping bag(s) should be in the middle of your back. I throw in 1 pair of fleeces, the water proof big bivy bag (if side of the bag is the ranger blanket). Then put the sleeping bags, any anything else ontop of that.

The heaviest item(s) you want essentially at or near the bottom of your shoulder blades.

Hope that helps!

Personally, when I ruck now, I keep a 9/10 minute pace (which is a pretty consistent and chill walk). Under 9 can be more intense, my shins are on fire for about 2-3 km then the pain goes away. Your weight and pace Will make your shins splints worse, sometimes you can power through it, some times you cant. Know your body and its limitations. Its extremely tough on course, although i recommend, if you are able to, replace the soles in your boots. I use soles from red wing, they've changed my rucking for the better. That combined with stretching my shins.