Trips to Northern Ireland have not been the most comfortable for the Tigers and everyone has already acknowledged the size of the challenge in the concluding pool fixture in the European Champions Cup this weekend.To say Tigers have been beaten on their previous three visits to Ravenhill is only partly true. In all honesty, Tigers have been beaten once. And very well beaten twice.   There was a 33-0 back in 2003/04, remembered as one of the blackest days in the club’s European history. A week later the pain was eased by a 49-7 win in the return at Welford Road, with skipper Martin Johnson running in a thrilling try on the day he confirmed his international retirement.   Then in 2011/12, Tigers beat Ulster 20-9 at home, providing some cause for optimism as we packed bags for the return. Sadly, with Toby Flood, Louis Deacon and Manu Tuilagi among the absentees, it was Ulster’s turn to bounce back in style, crushing Tigers 41-7 in front of a noisy capacity crowd.   Rivalry was renewed last season, with overlapping Logo Mulipola providing the try as Tigers took at the lead a Ravenhill stadium under redevelopment. The home side, though, made the most of their opportunities and were well in front before Owen Williams arrived as a late replacement for Flood and kicked a crucial penalty that rescued a point in a 22-16 defeat.   Unfortunately, an Ulster victory in the final pool fixture – Tigers’ only Euro defeat at Welford Road since 2006 – secured top spot for them and presented Tigers with a teak-tough quarter-final against Clermont Auvergne at the impregnable Stade Marcel Michelin.   The memories, therefore, have not all been good ones. But Ulster-Tigers encounters are nothing if not compelling. It makes for another tense tussle this weekend at the renamed Kingspan Stadium.