Only if the iPad is jail broken. This very annoying limit of 20MB is imposed by Apple (think yourself lucky, it used to be 10MB) for no really good reason. Perhaps it's to pacify the cellular operators, who knows? I get faster download speeds on 3G (over 5Mbps) than I do on broadband (2.5Mbps) so it's annoying to me too. Unfortunately, for a standard iPad, there's no way to disable this limit.
Tim