Strprw, I dont know if there still around but Imeo use to make an extension piece in Brass to extend the top of the 510 Atty tube. If you take a piece of the stock 306 sleeve 3/8" and put it on the 306 then slide a 510 tube over it from a blank carto your set up will be fine,,,, got what Im saying ? so its like the picture below but without the drip tip and cut the top of the 510 tube to fit.
I06 is about 8.44mm at the base, a 510 tube is a tad less then 9mm ID so you may have to make a thinner first section or just use a reg 306 mod like my picture shows.
That stock orange cart you may be able to use to do my 306/510 mod Strprw