The only time when you can save a particular version of SHSH is when Apple is still signing it. That means the latest iOS firmware Apple is providing at that time when you want to save it.

if you jailbreak AFTER 04/05/2011 but before 15/07/2011, u get 4.3.3 SHSH
if you jailbreak AFTER 15/07/2011 but before 14/08/2011, u get 4.3.4 SHSH.
if you jailbreak AFTER 14/08/2011, u get 4.3.5 SHSH.

The only time you can save 4.3.3 SHSH is when 4.3.3 is the latest iOS firmware from Apple (before 4.3.4 was released on 15/07/2011). You jailbreak at that point of time, Cydia will request from Apple server, Apple signs and provides, Cydia keep a copy of the SHSH in its server. Then using TU, you can copy the SHSH from Cydia into your own PC/Laptop so that you can use it to restore/downgrade to 4.3.3 ANYTIME you please.

Since you are trying to save an SHSH NOW, the iOS apple is providing NOW is 4.3.5, that will mean Apple will only sign & provide 4.3.5 SHSH, and that is the only one you'll get. Apple has stopped and will not sign & provide 4.3.3 SHSH from 15/07/2011 onwards (after 4.3.4 was released) so if any one of you that has a 4.3.3 ipad2, you can jailbreak ANYTIME but the SHSH availability depends on WHEN you do your jailbreak.

if you have an ipad2 that has 4.3.5 out from the box, then sorry to say, there's NO WAY for you to get any SHSH other than 4.3.5 bcoz you ipad is manufactured after 4.3.5 is released. Sell your ipad2 or stay on until somebody comes up with iOS5 jailbreak. good luck.