Thanks!

I found out, that I just have to correct the skin type and bytespp values, which I pass to .Skin and .SkinSize in the case that format is 8888 and bytespp is 3 -- I can always use the .pixels pointer.

[EDIT] Just for the record: if I create a bitmap during runtime and it is 8888, I can simply use finalbits (after locking) and if the size of the bmap is power of two; if it is 888 I have to do the stripping method I mentioned above (create array of 75% size and copy all contents from finalbits except every fourth element).