Need experts on 401(k)s and IRAs, non-deductible contributions

I’m looking for financial advisors, retirement experts, academics and plan providers with tips on making non-deductible IRA and 401(k) contributions under the new tax law. Prior to passage of the new lower income tax rates, what factors did investors need to consider in making non-deductible contributions? What typically tipped the balance? Describe the investor who was most likely to benefit from non-deductible contributions. How has that changed now that income tax rates are lower? Is it a big enough change to make a difference? Will this change the group of investors likely to benefit? What factors could derail a strategy put in place today? higher tax rates later? Higher inflation? Living longer or shorter than expected? How do clients react when you suggest these contributions? Do they take a lot of convincing? Or is it the other way — you have to talk them out of it? What else should I be asking? Requirements: I prefer responses by email containing usable content and quotes, and because I usually get plenty I rarely respond to ones merely offering a source for interview. Please include the source’s contact info, full name, title, firm and location.