Thanks. FYI, regarding your final FERS Supplement payment, I called OPM recently to verify this...since the monthly payments are paid in arrears, your final FERS Supplement payment will come with your OPM deposit on the first day of September.
In my case my final FERS supplement will come with my July 1st OPM annuity deposit, so I'll want to make the TSP change in August due to the shift of the TSP monthly installment payments. I assume you got the TSP letter in April telling everyone that all TSP monthly installment payments will be made on the 15th of every month starting this month. That sucks since I was very careful to time my monthly payments to come on the first of the month. I like having all money coming in early in the month, and going out late in the month. Leave it to the TSP to screw that up, but I can live with the middle of the month. When I eventually start collecting SS I think that will come during the 3rd week of each month (it's based on what day of the month you are born). The weird thing in my case is that I think I'll get two payments in June basically. The one I would have gotten on June 1st came early on 5/23 (as they'd forewarned in the letter, they sent them early due to the shutdown) since as far as they're concerned the payment date is on the 31st each month (but my bank doesn't get it until the 1st of the following month). So now the one I would have received on July 1st (but with a 6/30 payment date) will come on 6/15, I think, we'll see, I'm confused...
One good thing is that this shift in the TSP installment payments to the 15th will fix the problem where I wasn't getting any TSP installment payment at all in January each year, and I'd get two in December. I think they did that for tax reasons. Now they should come every month on the 15th.