I've really been focusing on getting the posterior third of my tongue on the roof of my mouth and placing a lot of force upwards with it. However, I have noticed when I do this, the front part of my tongue, or the tip, is generally not applying any pressure upwards. I've kind of ignored the whole "tip of your tongue right behind the front teeth" idea in favor of "posterior third of tongue plastered on roof of mouth". Is this really bad? I have a hard time getting both on the roof of my mouth and I have a natural aversion to having the tip of my tongue near my teeth due to years and years of tongue thrusting.
back third is the most important thing by far. it responsible for pushing the maxilla forward.
as your maxilla goes forward so does your jaw i.e your teeth are gonna go forward and up; over time this will make more room for your tongue so you don't get as much tongue thrust action
practice your tongue posture and do tongue chewing exercises and it will become easier to do both eventually
As long as the front of your tongue is sticking to the palate all the time while you are pushing the posterior third up that is fine.
Most likely the reason you hardly feel anything at the front is that there is plenty of space for your tongue tip to rest there effortlessly. Where as at the back your molars are blocking your posterior tongue and forcing you to apply pressure to get it up there.
You also might have a weak tongue making that effort feel even harder. Dr. Mew suggests doing an exercise called tongue chewing to strengthen it.
https://www.youtube.com/watch?v=ZNocCJNicrc
my story: http://www.aljabri.com/blog/my-story/