Yes this me, Paul Bryant builder of Exhaust systems.
And yes I do make a full system, see this page 
Viking Exhaust | Facebook for all that I build.
I can set the header up to suit what ever Silencer/Muffler you would like to use, or build one to your style/requirements.
With this complete 3 into 1 system as shown on my bike below (Red '06) K&N Filters and a tune to suit we are getting around the 160RWHP mark, approximately 33% over stock.
I think Dains muffler looks O.K. when it is mounted, I can't comment on the performance and sound as I don't know.
	
		
			
		
		
	
		
		
	
	
	
		
			
		
		
	
This photo shows my Header with a reducer to step down to the Stock Headers 1¾" tail pipe.
This allows this to plug straight into the Stock CAT (all models) or into any aftermarket rear end system that you may already have. D&D slip on's for example.
	
		
			
		
		
	
	
		
			
		
		
	
My header into a Rinehart Muffler.
	
		
			
		
		
	
	
		
			
		
		
	
My header into the Stock Roadster CAT and Silencers.
	
		
			
		
		
	
	
		
			
		
		
	
Paul,
Have you ever given consideration to building a can with a slashed end similar to the stock R3T?  I really like the look of the stock header and pipe but the restriction robs HP.  I would like to buy a full system that goes 3 to 1 (with cat box) that looks similar to stock using the same heat shields.  Too much to ask due to logistics of design?  I am not a pipe builder just a guy who likes the aesthetics of the stock, but wants to match the roadsters power.  Any thoughts?  
Cheers,  Paul.