In my opinion, and I still have a fairly young FF LB, tackling and strength are pretty equal when it comes to fumbles. However, tackling is only good for the impact on the RB. Strength is more important since it helps with breaking blocks, which you are going to need to do a lot since you are sacrificing speed/agility and keeping from being pancaked.
I have basically a hybrid built FF/Interception guy that is more experimental. I'm in the process of bringing tackling to 74 and putting all equipment on upgrades there and getting a fourth interception piece of AEQ. I'm hoping at plat he'll be around 90str/90tack/90sp
Billy McNuttshot (Lv. 46 LB)
Ht/Wt: 6'3", 238lbs
Experience, Skill Points, and Cash
Money: $0
Daily Salary: $5200
Skill Points: 0
Training Points: 0
Bonus Tokens: 4
Veteran Points: 0
Next Level: 210/1000
Attributes
Physical Attributes
Strength: 86.1 (+8)
Speed: 92.63 (+19)
Agility: 79.1
Jumping: 35.63
Stamina: 29.06
Vision: 52.1
Confidence: 25.06
Football Skills
Blocking: 17.5
Catching: 17.5
Tackling: 55.1 (+7)
Throwing: 9
Carrying: 8
Kicking: 8
Punting: 8
Special Abilities
Hard Hitter Abilities
Snarl: 1
Aura of Intimidation: 1
Diving Tackle: 1
Monster Hit: 5
Defense General: 1
Pass Rusher Abilities
Trash Talk: 0
The Glare: 0
Shed Blocks: 0
Swat Ball: 0
Big Sack: 0
Additional Abilities
Blitz: 0
Veteran Abilities
Heavyweight: 10
Power Tackler: 15