As also discussed partially in another thread, this seems to be quite problematic.
Thinking a little about it, it is not a really good system and has no real good motiviation to have something as "+" if you do the allocation approach.
If allocating, all the "+" does is imposing a minimum on a certain attribute, which is no benefit at all.
I would suggest to go back to the old ways and let the players add/subtract 5 at the end.
This might lead to 2 attributes slightly higher as 45, but given that you can increase attributes evevry rank once this time instead of 4 times total anyway, it is not such a big deal.