1. yes
2. no you wont lose damage, lvl 41's are actually quite fine
3. procs work at any level
4. likewise but it needs to be 41 if you want the other bonusses of the set to work
be patient, veeery patient. IO's around 40 tend to be low in stock and expensive (villainside that is)
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1) If i want the recharge bonus from 5x Crushing Impact, is the maximum level IO I can use is lvl 41 ?
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Yes. All the Crushing Impacts you want to apply towards set bonuses will need to be a maximum of +3 to your exemped level (38).
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2) If I slot all my attacks with lvl 41 Crushing Impacts, arent I losing out on a considerable amount of damage compared to slotting them with a lvl 50 set of C.I's ? or do you guys feel the bonunses you get make up for it ?
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Any damage you lose will be negligable since even with level 41 Crushing Impacts it's easy to get over 100% Damage. The other attributes will be more greatly affected (in the region of 5%), including Accuracy (pretty important for PvP). Play about with Mid's Builder and see what you can come up with.
Generally folks will leave out the Damage/Endurance or Damage/Recharge depending on the attack, and the attack's 6th slot can easily be a level 50 "Acc/End/Rech Mako's Bite".
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3) If I slot a lvl 50 Chance to build up in build up, will it proc or does it need to be <41 to proc
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Procs work at any level.
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4) Likewise, if i use Numina's +regen+reecovery, does it need to be <41 to work in Warby ?
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The Numina and Miracle +Recovery uniques act as "Procs" rather than set bonuses and work at any level.
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any other hints / tips would be useful, im not a noob to the game, I have 5 50's - I have never looked at PvP slotting before and I need a gentle shove in the right direction.
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Above level 32 (Warburg, RV, Arena) you won't need to worry about losing any enhancement effectiveness when exemped... but for Sirens Call, you'll lose a bit of enhancement strength. It works out at about 7% stripped off, so you'll need to add about 7% extra enhancement (eg. so you've got 107% Damage before ED kicks in) to be at 100% when exemped down to level 30.
For Bloody Bay, you'd need far more- about 27% - and so little PvP takes place in BB that it's generally not worth trying to compensate for that amount of enhancement loss.
Thanks guys, thats a great help, maybe i'll see you in a few days 
Well maybe not a full tutorial, but a few helping hints wouldnt go amiss.
Just need you guys to clarify a few things if you can as I'm not sure I have this 100% right.
I cant seem to find a Great guide on this, so i'll just pop a few questions.
1) If i want the recharge bonus from 5x Crushing Impact, is the maximum level IO I can use is lvl 41 ?
2) If I slot all my attacks with lvl 41 Crushing Impacts, arent I losing out on a considerable amount of damage compared to slotting them with a lvl 50 set of C.I's ? or do you guys feel the bonunses you get make up for it ?
3) If I slot a lvl 50 Chance to build up in build up, will it proc or does it need to be <41 to proc
4) Likewise, if i use Numina's +regen+reecovery, does it need to be <41 to work in Warby ?
any other hints / tips would be useful, im not a noob to the game, I have 5 50's - I have never looked at PvP slotting before and I need a gentle shove in the right direction.
Thanks in advance