Im going to tack on here and add that disregarding whether or not packing the tube facilitates further length growth, I think there is another important thing to consider, that being fluid build up and other skin related issues. From my time using tubes that were to wide to now switching to a 2in diameter pump I have at least some objective opinion on this. So lets break down the two options for pumping between a oversized pump and a fitted one.
1. Oversized; The pump being large enough in diameter that most likely no “packing” will be reached at any point through the tube from the head to even the base. This can also mean tubes that are to large to be packed unless the user starts with a smaller tube first. This will leave an even negative pressure surrounding the entire member. “Surrounding” as in there will be direct contact of the skin and the negative pressure inside the cylinder.
2. Fitted; The pump will be sized properly enough that with some engorgement the member will begin “packing” parts of the tube. This typically will start at the base, and leave areas further up the shaft and the glans still “surrounded” by the negative pressure.
I think we all already understand these premises, however I like to make sure all definitions are clear before continuing on to a point. What I think is important to consider here, is that any skin that is in (what we can define for this argument) direct contact with the negative pressure will be affected greater at the epi/subdermal levels than areas that are not. What I have personally observed is that areas in direct contact will see greater risk for Spotting(red spots caused by capillary breakage at the subdermal level), bruising or blisters (another epi/subdermal issue), and edema. Edema while not directly a subdermal issue, it can be argued that by wearing sleeves or other methods one can reduce the stress on the skin during pumping which can also reduce edema, so there is a moderate correlation. The second point of consideration is that while a “Fitted” tube will ultimately decrease the amount of skin in direct contact with the negative pressure it does not mean that those areas are not enduring a greater internal volume than during a typical erection. So while, yes, the areas where the tube has been packed will most likely not continue any further direct expansion outwards they will still be under the force of the vacuum for the duration of the exercise. For example if ones base-girth is 5.5in, were to enter into a tube that allows for them to reach a base girth of 6.0in before packing the tube. The user would still be stimulating 0.5in of outwards growth at the base, while at the same time limiting the base with further contact directly with the negative pressure. By doing so I believe are you not only limiting the possibility of adverse side-effects (spotting, blisters, bruises, and edema) to certain areas, but actually ensuring that the “packed” areas are being directly affected by increase in blood flow and tissue engorgement, rather than stimulating fluid and blood build up at a the subdermal levels.
My point here is that I think its far more beneficial to use a fitted cylinder no-matter if your goals are for girth or length. As by going for something in which cannot be packed (or can once edema has been introduced to the system) will mean your more likely introduce things that are non-conducive to ACTUAL growth. Spotting, bruising, and edema are all of which have 0 benefit to stimulating growth, and while are not inherently bad, they serve 0 purpose to the pursuit of expansion. While again the premise of using a tube that can be packed should offer some level engorgement, which will more than likely be tissue/tunica expansion, before then sealing off from direct contact with the negative pressure system, thus decreasing the possibility of continued non productive affects taking place.