Not a bad project as long as you have adequate help/equipment. I just finished replacing 14 columns on our wrap around. You will need jacks to lift the porch, etc. You may have to pre-order the columns to make sure that they are the right length. Make sure you use an aluminum plinth block at the bottom for ventilation as well as keeping the column from sitting right on the floor. Finally, and perhaps most important...be sure to prime the bottom of the column with two coats of OIL BASED primer. Following up with a coat of paint on the base won't hurt.

Hello, Building a nice screen room with tapered round columns is a bit time consuming but can be done. I've done a few on some historic homes. What I do is is align a piece of either 5/4 or 1 x along side the tapered column. I then hand scribe it vertically plumb, cut it so that it butts tightly against the column with its' slopes. The end result is a vertically plumb 1x or 5/4 jamb to create a square box in between the tapered columns to accomadate the new screen panels. Normally all the tapered columns are the same. So once you make one attachment piece to a column, you ccan copy them for all the rrest. Now you have a square opening to calculate your screen panels that would be installed in between. I make my own cedar screen frames and run screen spline tracks on the table saw. Of course I prefinish all the pieces and parts before assembly. If I can be of further help, please email me with your thoughts. All the best, The PorchGuy Here is a link that might be useful: My album

The simplest way to calculate that is you take for 1' of height =1" of diameter so if you have a height of 6' it would be a 6" round or square column.

Without pictures tough to tell, so the answer is maybe. How visible are the porches from the front of the house? How large are the porches as scale is more important at times.