TI frame design question

Hi all, does anyone have any tips for how to do a long seat tube on a TI gravel frame that accepts a seat mast topper? How to reinforce the TT/SS junction? Normally bikes are welded with a thicker :collar" at that area but what can you do if the tube extends up another 6 or 8 inches? My guess is to use a much smaller diameter tube like 1” or so for the entire seattube/ mast. Any tips on that would be really appreciated! Thanks