the bump stop and boot top. Then you can trim/remove them to gain compression
Agreed. I did this on mine and it helped a little, as did significantly raising the ride height. However there is more to be gained with improved dampening.
To help illustrate how the dampening rate will affect this bottoming issue, I can relate two experiences I've had (there have been many others, but these are more to the point). Keep in mind that at least 90% of the countless custom vehicles I've built were for street/road use, and only a couple of true track/race ones. So I am not an expert in setting up a race suspension. These experiences pertain to normal street driving, and that will differ greatly depending on your local road conditions, driving style, vehicle weight, and many other variables.
Example 1: I like a low ride height, primarily for the 'look'. When I lowered my X1/9 on the coilovers discussed here there was still a couple inches of travel available (with some of the bump stop removed, as discussed above). But they still bottomed out despite the stiff springs (mine have the same springs as Carls, 165/225 ). I swapped to my coilover modified Konis, with even softer springs (150 front, 175 rear) but MUCH firmer dampening. The Konis are built from their regular street struts and are not shortened, having the same travel as the first coilovers. With the sofer springs, but much firmer dampening, and set at the same low ride height, they did not bottom out and the ride was great. However keep in mind there are other differences between the two sets of coilovers, so I cannot say that all of the result was due only to the dampening rate. But I believe it is the primary reason for this particular issue (bottoming out, poor ride).
Example 2: My "shop truck" is a customized late model Ford F150. When it was fresh off the showroom I began modifying it. One of the first things I wanted to address was the really high ride height and poor ride. The suspension comes with very soft springs and dampeners (especially for a truck) but a lot of travel to compensate for loads. At the time there was very little aftermarket support for the (then new) design of front suspension, with a coilover type of struts. So the best I could get was shortened stiffer springs to fit onto the stock struts. The dampening on the stock struts was very soft, so despite the much stiffer springs they bottomed out a lot and the ride was terrible. A couple years later I found a company that started making replacement front struts for this model. They have great dampening (significantly higher than the stock struts) and allow for spring height adjustment, but uses stock type springs (not the universal coils like many coilovers). These struts are the stock length, and can raise the stock ride height as well as lower it. So I installed the stock (soft) springs with these improved dampeners, set to the lowest ride height - which was actually much lower than with the prior short stiff springs. They do not bottom out and the ride is terrific. The primary design of the two sets of struts is the same, with the internal dampeners being the principal difference.
Although this is not intended to be a scientific finding or professional explanation for the result, it does illustrate how dampening will affect not only ride quality but things like suspension bottoming. In both cases increased dampening combined with softer springs (and lower ride height) prevented bottoming out compared to similar setups with less dampening but stiffer springs, and it also improved the handling and ride. Furthermore the difference will become even greater as the soft dampeners wear out (as mine have), reducing their effect significantly.
I am not saying that removing the bump stops won't help, it did a little with mine. But I believe there is another issue that needs to be addressed with these coilovers in order to make them work well. Even at a much higher ride height setting (to prevent bottoming) I found the ride quality to be lacking; the springs are too stiff for the available dampening rate. Considering the same coilovers are available with other (improved) dampeners, is it possible to buy the better inserts to replace the standard ones in the Hydrosports? Thanks.