Well, I've tried many menthol juices and the only one I like is Vapers Choice Kentucky Menthol - but it only comes in VG (100%) - so I too have been sorta mixing and trying and mixing some more - cool mint is just too minty for me - and I found that 1/2 and 1/2 mixes are also too strong - so would suggest for you that try a small amount of menthol with say 3/4's
tobacco for a beginning - then add more of your crystals as you up the anty so to speak.
Re-reading your post and my reply - I had mis-read yours in the beginning (didn't see 'concentrated') - sorry - but perhaps others viewing would find my 2 cents worth of help? lol