I don't know how many of you use a filter in front of your convection blower. I made up something that may be useful for some. I bought 2 pieces of duct work parts, put them together using duct tape to cover sharp edges and inserted a filter. Its installed with the original screws at the blower motor. Works great!
If you look at the third picture, you will notice a floor register. That is running under the crawlspace to the exterior. This provides fresh air for the convection blower and the combustion blower. This also allows some return air to mix in. Thanks for the compliment!