Orifice Height
You might hear a number of opinions on this but we think a clearing of your "mindset" will allow you to understand that this should not be an issue for anyone.
Height - our view is this: it does not matter one bit if you are using a wheel that has a round orifice (not a delta style which you will find on Majacraft wheels). The round orifice allows the spinner to have the yarn approach the opening of the orifice at any angle. This can be straight into the orifice, or any angle up to a 90 degree turn of the yarn as it enters the orifice (not a likely angle, but it works). So if you can imagine holding the hand that controls the twist at an extreme location (for example, at 12, 3, 6, or 9 around the "orifice" clock), you will find that it works. A normal, comfortable angle is somewhere in a "cone area" out in front of the orifice.
Spinning takes place at your hand, not in or at the orifice. So locate your "spinning hands" anywhere you like that is comfortable - in front of you, to the left or right; any where. Your hands do not need to be near the orifice when spinning and we would even encourage you to keep your hands away from the orifice as this will tend to have you sit too close to the wheel or to bend over as you spin.
Sit back and get comfortable in the position that makes it easy for you to treadle. Now that you are in a comfortable position for spinning - spin. If your hands are 6" to 12" or 18" from the orifice, that is OK. If your hands are left, right, above or below the orifice, that is OK As you see, the height of the orifice is not important (if you feel a need to have your hands just in front of the orifice, you need to correct this). With your hands in a comfortable position, let the yarn go to the orifice at any angle that results.
Consequently, height of the orifice is not important.