On my last partigyle, I made a barleywine in combination with a jalapeno porter. For the porter -- which would actually be classified as a "brown porter" and not robust -- I steeped additional black, chocolate, and roasted malts, and then found the beer was still too thin and wimpy, so I actually steeped the equivalent of 3 times as much as I thought I needed, and that seemed to do the trick. And then I added jalapenos on bottling day, approximately two per gallon if memory serves, which had been soaked in hot vodka for 5 hours, and then, of course, any perceptions of being a wimpy beer disappeared ENTIRELY, and in fact it was one of the most fantastic and most loved beers I have ever made. Although, I really enjoyed the beer without jalapenos as well, and saved a few bottles for myself. Very yummy brown porter in its own right, but everyone loved the jalapeno version as well.
In future, yeah, I think I'd add more crystal malt to the second beer in order to give it some more body and muscle. Otherwise, it can indeed turn out sort of watery and wimpy. Jack up all your specialty malts, and crystal, by a couple notches, and you'll be set.