Plastic Royal Marine Light Infantry?

I've been painting the downstairs hallway today rather than the wargaming figures, so there's been no time to get any more progress made on the Beja. However, I have ordered a box of Perry Zulu War British infantry, with a view to using them for the Zulu War of course, but also as potential basis for some conversion into Sudan War Royal Marines. This would involve pinching the helmet heads with puragrees from the Afghanistan British set, which is the easy bit, then adding loose trouser bottoms to the legs with green stuff or plastic putty, which is a little less straightforward. It would be worth it, however, as the equivalent in metal of a plastic box set would be at least fifty quid, compared to under twenty for the plastic fantastic option. If it doesn't work, I can always start a Zulu War project too!