bussproof's default least node height setting

Question

I noticed that bussproof's node height is dependent to the height of the formula in the node.

for example, nodes like "p" , "q" and "r" have shorter height than "l", "b" and "d" because the former formulae have shorter vertical length.

I want to fix the nodes' least heights as I expected using the bussproof's option setting functions.

for example, in the cases of p, q, r, those should have upper padding so their upper horizontal line(expressing judgement) aligned as the same with the other derivations so that simliar depth of the derivations are horizontally aligned on the same line in a page.

of course, I can add some invisible string in all nodes so that setting they have the same least height, but I think it's not the tidy solution.

\[
\AxiomC{D}
\UnaryInfC{$p$}
\AxiomC{D}
\UnaryInfC{$p'$}
\BinaryInfC{$\phi$}
\DisplayProof
\quad\implies\quad
\AxiomC{D}
\UnaryInfC{$p\phantom{'}$}
\AxiomC{D}
\UnaryInfC{$p'$}
\BinaryInfC{$\phi$}
\DisplayProof
\]

Answer 1

I think that it's better to add more space around the inference line and then create a zero-height box for the prime. This produces a nicer looking display than your version using \phantom. Btw, when you're asked to provide a sample document, it should be a complete compilable one like this:

\documentclass{article}
\usepackage{bussproofs}
\usepackage{amsmath}
\renewcommand\extraVskip{5pt}
\newcommand*\Prime{\smash{'}}
\begin{document}
\[
\AxiomC{D}
\UnaryInfC{$p$}
\AxiomC{D}
\UnaryInfC{$p\Prime$}
\BinaryInfC{$\phi$}
\DisplayProof
%
\renewcommand\extraVskip{2pt} % back to default value 
\quad\implies\quad
\AxiomC{D}
\UnaryInfC{$p\phantom{'}$}
\AxiomC{D}
\UnaryInfC{$p'$}
\BinaryInfC{$\phi$}
\DisplayProof
\]
\end{document}