It'll work.

You may need the 8mm shims or DIY shims to keep the Back Rollers from rattling on the smaller diameter Al rod used in Blackburn racks. Duct tape or similar is a good jury rig for this job.

Inexpensive Al racks will work as long as you load reasonably and stay on pavement. Heavy loads, especially when combined with off-road routes demand a stronger, more enduring steel tubing rack. Tubus is what you really want. Best deals I've found come from 20% off sales from wiggle.co.uk, purchased in $ (they cheat on the GBP conversion).