Unfortunately, the lower cross brace does little to help roll stiffness of the Tiger. The x-member is the tie that ties. Unless you are into serious racing, I wouldn’t worry about its absence. Removing the brace does have a few degree improvement at road speed.
Forget all the trick radiators. The Tiger needs air…lots of it. Focus on getting air. Virtually any modern rad will function well. Even the original rad type gives good performance.
Fans. The best we tested is Derale #17015 or an Imperial. They are cheap too. How’bout 623 CFM with a stock or Flexlite fan VS 1195 CFM with a Derale. Almost double. Numbers do not lie. Beware of the Flexlite #1314 or is it 1413. Whatever, The blades fatigue crack. The Mustang Fan is OK if the original 15" dia is maintained. But they have become collector items for some stupid reason when there is actually a cheaper better alternative. It is imperative to maintain a 15" dia fan with a shroud. Move engine but do not cut fan.
Read about the cooling studies Chuck King and I did at https://www.teae.org/cars/cooling/cooling_article.html
This is the only scientific study ever done on cooling a Tiger. We have the cooling enhancements in our Tigers as do a lot of others. In my car, I DO NOT use any electric fans, have air conditioning, use it for towing other cars and it can idle in 104F heat with the AC on and blow cool air.
Be Kool 8)