I watched this a few weeks ago when the lawsuit was first publicised. Senator Shelby from Alabama is so infuriatingly transparent. I mean it's so obvious he has no real interest in lowering spending. ULA is effectively a jobs programme for his constituents and the rest of the nation pays dearly for it.

How do two people, neither of which is a senator on the relevant committee, go head-to-head in a Senate hearing?

Senators are not experts on every topic that they govern over, so they solicit advice from experts.

...and In this case 2/3 of the experts called were/are competing for the government's business.

Edit: Strike that ... 1/3 of the experts is asking to compete for the government's business. 1/3 already have a monopoly for this work.

I'd say that's pretty "head to head".

As long as "head to head" includes interaction mediated by the Senator currently recognized and the chairman of the committee. In my opinion this mediation eviscerates any "direct conflict" between two people who are not senators.

Agreed. However the "experts" are not allowed to address each other individually. Senators ask a question to an expert and the expert addresses his or her answer to the Senator.