Making dsRNA constructs in vectors? Hauge and colleagues report a one-tube, ligation-independent cloning method. If you're making your own constructs for in vitro or in vivo work, might be worth taking a look at their strategy.
Hauge et al. (2009) Single tube, high throughput cloning of inverted repeat constructs for double-stranded RNA expression. PLoS One. 4(9):e7205.