It's definitely possible.
The -4 on RC means you have good reading speed and comprehension, and reading speed is often what kills people on improving significantly. So, your in good shape starting off and I suspect that your LR score will come up extremely fast. You read well, so it is likely that you simply didn't really understand what it is that the test wants from you in that section (it takes some adjustment, that's for sure).
-10 on LG is also a good starting point, and that section is the easiest to improve.
Given that you nailed a 730 on the GER you probably don't have any test anxiety issues, so I'd say you aren't deluding yourself at all. It will take some hard work tho
