Ikelite Modular Kit vs Fixed Port

[rgilkes]

Hey All,

I have an a7RII and FE 16-35 f4. Ikelite recommends either the modular 8" dome port w/ 5.1" extension kit or the fixed dome port for lenses 4-5". Obviously there's a pretty large price difference. Is this solely because the modular kit can be adapted for multiple lens sizes or is one optically superior to the other?

Thanks!