I think you have it backwards. Mushrooms in this study have a pKi of 4 so Ki = >10 micromolar binding affinity. So you need a dose higher than 10 micromolar to fill half of the receptors with psilocin.

This article suggests that all of these drugs can potentially bind to the 5-HT2b receptor, but LSD binds more tightly than psilocin. Is this a concern? I don't think so. When Fenfluramine/phentermine drugs were pulled they were found to cause valve problems and resulted in them being removed from the market. People were made aware of the 5-HT2b receptor and there was a study that showed correlations between fen/phen and valve issues due to this receptor. One drug was found to be beneficial for heart disease and didn't associate with valve problems. That drug was lisuride and it remained on the shelf. Based on the data obtained from your paper we can see below that lisuride binds more tightly than LSD. I'd argue daily LSD and psilocin aren't as dangerous as you're making it out to be. Paper I found regarding the above

5ht2b: 4.00 DOB, 4.00 MDA, 4.00 Aleph-2, 4.00 2C-B-fly, 4.00 2C-B, 4.00 TMA, 4.00 psilocin, 4.00 TMA-2, 4.00 2C-E, 4.00 2C-T-2, 4.00 4C-T-2, 4.00 MEM, 4.00 DOM, 3.97 mescaline, 3.93 6-F-DMT, 3.91 5-MeO-DIPT, 3.91 DMT, 3.88 DPT, 3.70 DOET, 3.64 MDMA, 3.48 DIPT, 3.32 5-MeO-MIPT, 3.13 DOI, 3.11 LSD, 3.01 lisuride, 2.72 cis-2a, 2.17 SS-2c, 1.81 RR-2b, 0.69 5-MeO-DMT; 0.00 salvinorin A; ND: 5-MeO-TMT, ibogaine, EMDT, morphine, THC>

I think it's sloppy to suggest Alexander Shulgin had valve surgery due to 5-HT2b receptor activation. You can't know that nor can any doctor. As cardiovascular disease is a leading cause of death we don't know the etiology of his disease is in fact LSD or mushrooms.