Why not just use the most current version? Don’t think it makes much sense to go back to such an old and less functional firmware. Oldest version available 1.82, though.
What part of the 1.7 are you wanting that the latest version dose not have?
OR
What part of the latest version are you getting stuff with that maybe we could help or assist you with?
I can’t imagine, why you want to go back to an old firmware, but I can send you the file 1.71 or 1.73 or even 1.40. If you want it, just send me PM. But this will only work with the desk. You will not be able to install the iPad app for any old firmware version.
Are you using an iPad on old firmware or an iPad which has a jailbreak as this would mean to retain functionality you wouldn’t want to upgrade?
I can think of no other reason not to upgrade.