A.H.Benade and Lew Paxton Price recommend a wall thickness of at least 1/8th inch at the voicing or it will be very difficult to generate oscillations. I find this true in my experience.
The thickness of the Tube Material at the voicing (ID to OD) can average between 1/16th and 5/8ths inches, but this is not a set "rule". Sound waves travel through solid materials faster than air (Young's Modulus). This means that the more mass/atoms a material has, the faster sound will travel in it. Hardness is also a factor (harder/faster).
Example: A concert german silver flute is more dense than a wooden flute and will favor high frequency harmonics. The wooden flute will attenuate more of these frequencies in it's softer mass and favor low frequency harmonics.
I find it best to keep the thickness at the toneholes to a minimum to reduce any flat tone at higher registers with more internal pressure. Higher aircolumn pressure pushes up into deep toneholes and increases internal cubic volume leading to flat tones. I try to stay at least a 16th though, or the finger pads intrude into the bore.
Tuning Slides: The prefered metal is German Silver (60/40-copper/sterling silver). This metal is cheap and once oxidized (reticulation) and polished, it resists corrosion. Bronze and Brass are used, but these copper alloy metals produce toxic verdigris (green copper oxide) when corroded.
You didn't mention "Bore Perturbation" but... Restricting the bore just above a tonehole will increase aircolumn velocity and raise pitch. Conversely, increaseing the ID will do the opposite (E = 0.5mv2).
The combinations are Legion here, so I have generalized. questions? vengeful retortes?
