Is the 1320 STC Dead?

I brought this up at the last convention and was surprised by the lack of excitement about this. Since MOSAIC now lets someone flying as a sport pilot legally fly an Ercoupe 415D, why wouldn’t I convert my C to a D and get 80 additional pounds?

Consider this:

1320 STC - I have to make sure the orifices in the oleos are correct. I must have the ¾” trim tab. My elevator up travel must be limited to 9°. When all is done, my new gross weight is 1320 pounds. 

Upgraded to D - I have to make sure the orifices in the oleos are correct. I must have the ¾” trim tab. My elevator up travel must be limited to 9°. AND the sheet metal directly over the cowl tank must be stainless steel. When all is done, my new gross weight is 1400 pounds. 

So the pro of upgrading to a D is an additional 80 pounds of legal gross weight and the con is the cost of replacing the skin over the cowl tank with stainless steel. 

The con of the STC is its cost. The conversion to a D model is by 337.

Which method would you choose to add the needed pounds to the legal weight? I’d go D conversion without a doubt. And now when shopping for a plane I would definitely consider D models - even prefer them!

If there is a good reason to go the STC route that I’ve overlooked, please let me know! And I know that 9° of up elevator requires faster landings. You can always go with a split elevator. But the limitation applies to both of these solutions, so it doesn’t matter.