A Windows 7 installation with updates is typically under 20 GB, probably over 15 GB.
I have an 80 GB SSD with 55 applications and have never used more than 30 GB of that 80.
You can save space by turning off hibernation, reducing the space devoted to System Restore, and either reducing the page file or putting it on another drive.
I don't think you'll get much encouragement about fiddling with junction points or symbolic links.
And probably not much encouragement for using RAID with a Windows 7/SSD laptop.
I'd install apps to the SSD up to the level of maybe 27 or 28 GB and then go to the 750 GB HDD.