Our first time to Vietnam and this area of Central Vietnam. We found this company under tours with good reviews and Mr Vu's company was offering multi-day tours and customised if required. So some back and forth emails and a slight change to one of his 5 day packages we visited Hoi An, Hue, the battlefield areas, DMZ and the one area we wanted included - the caves around Dong Hoi - he fitted into the itinerary They were spectacular and whilst the history of Hoi An and Hue was good to see, we particularly enjoy natural scenery around Dong Hoi.
Whilst it would be nice to have Mr Vu as your guide if you had a particular interest in history of the battlefields and the DMZ, we were not disappointed with Mr. Tam (our guide) and Mr. Thang (our driver). He may not be as experienced as Mr. Vu but we found him sufficiently knowledgeable in all our questions on Vietnam and the history of the various areas we visited. 
On our way north Mr Tam called into his office at Dong Ha and we met Mr. Vu which was nice.
Mr Tam is a reserved man but we found him engaging and personable and thoroughly enjoyed our time with him. He is an asset to your company Mr Vu.
Mr Thang likewise is a reserved man but a good driver and always happy and keeping us well supplied with water.
The whole trip was made most enjoyable by Mr Tam and Mr Thang - we had no worries as they looked after us the whole time.