Well... TMO is not much heavier than the Stock game... it doesn't add much to the roster, and since the SH4 game is "dynamic" in its loading (only loading what is within approximately a 30km area), the size of the campaign is not an issue. Run the LAA app again, using the Intermediate mode, load the SH4.exe in it again, and make certain that you see under the "LAA" column a "True" setting, while the "Original" column would show "False".
You should not be having troubles with SH4 on a computer like yours. It might be that you'll have to start all over again, and un-install Silent Hunter. When you go to re-install, make certain that you are NOT in the "Program Files (x86)" folder, or any other Windows "protected" system folder, so that JSGME works correctly when activating your mod(s). You also want to make certain that you install the game's version of Windows' DirectX v9.0c so that all the graphics function correctly. That will not ruin the current DirectX on you machine. Also, be sure you delete "C:\Users \YourName \SH4 \" and all of its sub-folders to clear that data. Then run JSGME, and put Ralles Mod Pack in MODS and start building it again. If it still doesn't work well, there has to be something running on your computer that is "stealing" clock cycles. You could use Task Manager to see what's running on it now, and how much of the computer any particular app is pullling...
