After the new patch I've found myself going for the 5-man upgrade immediately before my second IS. I will get 3 ISes in total, while saving myself a guaranteed 2x28=56 MP. 3x 5-man IS can stand up to any axis infantry unless you get suppressed.
Also How do you feel about sniper micro? I usually get one sniper for MGs and elite infantry, but going for more has a micro tax especially with heavy indirect fire and counter snipes. Your guide mentions aggression, but I find that easier in terms of preservation with ISes and grenades. Against any decent opponents, they will have AT before your first tank anyway so do you feel it's absolutely worth to rush every second of it?
I'm not sure that 56 manpower is worth the fuel investment that early for 5 man squads.
Snipers help you deal with Kubels, MG42s, Sturms, and any light vehicle that can threaten your ally's M20. The UKF sniper is amazing.
My play-style lends itself towards preferring snipers over IS but depending on the map and situation you can get IS over Snipers. If you feel like having multiple snipers will put too much micro pressure on you, play with the IS instead.
This patch it is probably not worth it to rush Centaur if they already have 2x PaK or a Jp4 on the field.