A physician defers the maximum into a hospital 403(b) Plan, and then makes a contribution to his own separate PSP to the maximum Section 415 limitation (without considering the 403(b) plan deferral). Permissible?

He owns the business that sponsors the PSP? The 403(b) plan is treated as sponsored by him, not the hospital, for 415 purposes, so the two plans share one 415 limit.

Yes, he owns the business sponsoring the PSP.

I see that rule--that his 403(b) account and his co.'s DC plan are aggregated for 415 limit--in the new 415 regs. It appears from the old regs that that rule is unchanged and has always been the same, correct?

I believe so - IRC 415(k)(4).

IRC Section 415(k)(4) takes us back to 2000. I've now discovered that the old reg (Treas. Reg. Section 1.415-8(d)(2)) dates to 1980.

Thanks.

I am sure you know that the 402(g) limit is personal. However, the 457 limitation, including for elective deferrals, other than in come catchup situations, is purely additional. Also, a 457(f)/409A has no limits, but design constraints make it less likely to meet the doctor's needs.