I want to try a27.5 front end, is the old Blur a good frame for this, or should I look for something else?
The LT had a super slack seat angle, so if you are big for the frame size (I was as they only went up to XL), I'd say that a mullet setup would make that worse still. It would climb like a wandery thing and you'd be forever perched on the nose of your saddle.
To be fair, I never liked my LT mainly because of this. I replaced it with a TRC as soon as they came out, and that was a great bike (still running with one of my friend's son).
Whack the figures into https://www.bike-stats.de/en/geometrie_vergleich then make the necessary changes - it'll give you an idea (on paper) of what effect mulleting will have. In reality I'd expect pretty much what fat-boy-fat says above: the already-slack STA will get even slacker, making it backwheel-happy.
ok, i see what you mean.
i;ll have to look for something else