Hello. I'm a beginner and had exactly the same issue. I noticed though that when I was sat down my guitar was at a certain hieght on my chest, when I stood up it was a few inches lower. I shortened my strap to lift the guitar and hey presto it was 95% better. Still not the same as sitting down but at least I can reach the chords etc I found easier sitting down. Simple solution for me so might be worth a try.