Acryllic sheeting is very similar to plexiglass, but has a clear to solid coloring scheme as is not used in same situations as plexiglass,,,plus I believe that its alot cheaper than plexiglass...

Plexiglass is about $15-20 for a 3x3 sheet, I paid $10 for an 4x10 sheet...

MDF is not as solid as oak, but it is solid enough for speedbag platforms...