I'm also wondering if it's worth buying the one with 5 screws even though I would probably not use all of them. I just need a bit more of expansion in one side where there is some crowding, but maybe the middle expansion would fix it after all. Also, now the website is back selling it for 229,99 and it was 169,99 euros (60 euros more!). I wish there was competition or someone selling something similar to the expanders we hear it's better like the homeoblock, biobloc and so on... But I'm actually not sure if they are really better because sometimes I think that taking tongue space actually would allow for an even greater force from the tongue in the palate (if you are intentionally pressing) to expand upward than it would be able to do if the tongue was in a larger space and fully stretched. Someone please explain if I'm wrong but I think this is logical: if your tongue muscle is compressed in a small space, you can apply more force than if it's fully stretched, right? Just be sure to keep pressing the palate also when you take off the device and I guess it's all fine.
It's probably true to certain extent, but in the end the amount of force tongue can apply in any position is not a lot compared to the static pressure from a palate expander.
As for the additional screws, I have my own doubts about their usefulness for expansion. There's only one suture the palate can grow from, which is the mid-palatal suture. Anything that pushes and keeps the two halves of the palate apart from each other should do the trick. Additional screws won't provide additional benefit for expansion, but they may be helpful in guiding crowded teeth to a more optimal alignment during the expansion process.