Link to post from developers
http://www.ppcgeeks.com/unified-rom-...007-t4174.html Caution: If you decide to try this, you'll have to use a different extended ROM than you have now - the old one you have will overwrite some newer files (incl. SD-related dll's) in 3.5. Look for a newer Sprint ext rom in this forum, or wait a few days for a Sprint installer after the 3.5 RC goes final soon.
What makes your device unstable (and mine when I ran the same config as you) is that AKU 2.0 is buggy. (Look at AKU 2.0 like Windows 98 or ME, and 3.5 like 2000 SPx or XP SP2). Sprint should have at least released 2.2 to their customers.
The ROM the developers are issuing is not 'custom' like many of the others you see. It's a stable base ROM that others will use to do their own customizations.