I'm 6'3" with legs that go all the way up.
This reply got a bit lengthy on how I went about the whole thing, so bear with me and I hope this makes sense to you.
I've rebuilt my whole putting stroke and stance over the past couple of months. First of all, I changed my grip, the way I hold the putter. Previously I used the same grip as with my other clubs with the grip resting on my fingers. This grip made the shaft lay quite flat leading the toe of the putter hanging in the air or me moving my arms away from my body to compensate for it. The grip also caused the occasional turning of the wrists as there was nothing to stop that. It (and the shaft being shorter) also made me hunch too much over the ball and put my eyes outside the line of putt (in other words and exaggeratedly my nose was over the ball), which is a no-no. You need your eyes on top of the ball or slightly inside the line.
Now I grip my putter so that the grip runs pretty much through my index finger and the life line in my palm. The shaft is aligned with my forearms, the putter sits flat against the floor, my eyes are on top of the ball and I'm standing more upright with my arms connected to my body.
How I determined the correct length was by standing up straight against a wall, with heels, buttocks, shoulders and the back of the head against the wall. Then I took a step forward, bent down from my hips and let my arms hang freely, connected to my rib cage. You want the putter grip in your hands in that position. Then you just need to get the correct shaft length and lie angle.
What I had was the old grip I had cut off and the two-ended shaft extension bit that was really long. I inserted the extension into the putter and the grip on the extension. It allowed me to check all the possible lengths from the original 35" to 40"+. I checked the length I felt comfortable with several times, tried moving the grip further up or down the shaft and always came back to around 37".
So, if you want to do it right, ask the pro shop to cut the old grip so that it can be used later on to check the length of the putter and buy an uncut shaft extension. Or do it in the pro shop with the pro. Move the grip up and down the shaft until you get it right. Just remember to do it with your golf shoes on and make some putts to ensure you like it. The correct length might not be 33" or 34" but maybe 33.75" or 34.2" and you can get the shaft to those lengths, it's just a matter of cutting the extension to the correct length.
As for the grip itself, I have long fingers and all the online grip fittings tell me I should use midsize grips, which the Winnpro X 1.18 is. The normal Golf Pride Player's Wrap worked with the way I held the putter previously but for my new technique, it's just way too small for me, especially with the added weight beneath the grip. I have to say the bigger grip doesn't stop me from turning my wrists, I need the added weight to remove the issue The original Winn grips that came with the Bettinardis did wear down quite fast but these are a bit different and the one I've had on the C-01H has held up well for several years.