Are you jailbroken? I recommend AppBackup. Install, open it up and go to the game, tap it and choose backup. Then use putty or winscp or whatever ssh program of your liking and copy it to your computer so you have a backup. (PM me for a tutorial). After this, install the new version of the game, open AppBackup scroll down to the game and tap restore!
(this is how I always transfer game saves from upgrade to upgrade. Maybe there's an easier way but this takes all of 3 minutes for me and it's worked 100% of the time for every single app store app ive ever used)
Edit: I made some changes to my post with the assumption you will not be restoring your entire phone which is what I originally thought.
You can just save it to iCloud or openfient just go to game options in a space station, then save game then click on the iCloud or openfient save option (which ever you want) and press save. Whe you open it in hd you just press load game then choose that save.
i know that you're only being a good guy here, what you are suggesting is different from what this guy wanted. this guys wanted to tranfer his save game from SD to HD. not from iphone to ipad just like what you are saying that it is what you did and it works for you ofcourse because he wanted another thing from what you did.
if any of you finds a way to transfer from SD to HD please tell me. icloud and OF only transfer from the same. SD to SD HD to HD.
Actually I'm pretty sure it does use iCloud, at least try the latest version of GOF2 sd/hd. I know because I transferred my valkyrie save from SD (which had valkyrie then) to HD (where valkyrie came out later) via iCloud, in my iphone. Too bad it's dead right now so I can't verify my claims.