As someone who has played with flygon X vs SP, its great card, don't get me wrong there but here the thing..when you playing sp, most of time there slap down a Lucario GL that makes normal flygon's weakness x2, then they bring up with luxray, then garchomp X then takes it down...with a 160 dragon rush..unless you somehow how can get the two out before there get that garchomp X out and have one of those flygon ready for a extreme attack after other gets taken down..I have tried it, its not easy..a flygon X can single handley destroy a sp deck if that X its out and ready for an extreme attack it going start picking off luxray, chomp, uxie etc..they know that..so there not going even let flygon live once it hits the field...trust me i know all too well...and it going even harder get out without claydol. if you lucking you own trainers and have relie on BTS and supporters to get that x out by t2 or 3. it just not that simple vs sp...I hate playing sp like the next guy..if going to run flygon x and vilepume, you going need fast and hard hitter to by you some time to set up..
now if you ran you own garchomp C with you flygon X..that may work, because now have 2 things that you can counter Garchomp with..you just can't have mindset that you going counter everything..you have take you hits and make smart moves..